What are the chances of Apple botching a battery replacement?

Apple provides hardware support for models for five years after Apple stops selling the products. So yes, I would say they will still have plenty of first generation SE service replacement units available.

A replacement may well have iOS 15 installed on it when received, but that depends when the service unit was set up. It could have an older iOS release on it.

Obtaining service for your Apple product after an expired warranty - Apple Support

icwvx wrote:

Battery replacement needed, iP SE 2017

Was told if damaged in repair a replacement would be provided.

Doubt they would have a 'direct' replacement.

Would rather live with the battery state than give up the SE.

Absolutely they have replacements. The first generation iPhone SE was discontinued in 2018 and Apple pledges hardware repair support for at least 5 years from the last date that device was manufactured. It's listed right here:

iPhone Repair - Official Apple Support

iPhone SE repair costs in the United States

Out-of-warranty prices apply only to repairs made by Apple. Apple Authorized Service Providers may set their own prices. 

Other damage (out of warranty)

iPhone SE (2nd generation)$ 269

iPhone SE$ 269

Apple will build up a stock of repair iPhones initially and as they're in production, plus using refurbished devices as service replacements. Service repair replacement iPhones will have a model number starting with an N, but where they should be functionally identical (model, color, storage capacity, carrier version) to the devices they replace. As they receive exchanged iPhones for service replacements, they will then send them to be refurbished as best they can. Maybe a good screen assembly here, a logic board there, a case somewhere else. Of course some can't be salvaged. Maybe cameras get reused. They might also use some new parts to rebuild them - especially batteries since all service replacements have a new battery. Apple also gets trade-ins. Since they don't sell many of the devices they receive any more as new, where do you supposed these go? Heck - there's even a chance that many devices that are returned within the 14-day return period just get a new battery and become service replacements after getting checked for condition.

But yeah if there's some issue where someone's hand slips and the logic board is damaged, the "workmanship" pledge means they'll just give a service replacement and take the phone that they damaged. But for that the key is that the exchanged device better be backed up, because Apple never guarantees the integrity of data. Even when they do 100% correct repairs or battery replacements, they'll test and have even been known to reset a device to factory condition for one reason or another. And if it's a service replacement, that will come with a 90 day warranty, while a battery repair itself only comes with a 90 day warranty on the battery.

These are the general service terms, but this is pretty much the same for Apple Stores or AASPs.

https://www.apple.com/legal/sales-support/terms/repair/generalservice/

3.1 Service Warranty. For all service orders, Apple warrants that (1) services performed will conform to their description for ninety (90) days from the date of service, (2) except for batteries described in the subsection below, all parts or products used in service will be free from defects in materials and workmanship for ninety (90) days from the date of service, and (3) batteries installed as part of Apple’s battery replacement service for Apple portable Mac computers will be free from defects in materials and workmanship for one year from the date of service. This warranty is an express limited warranty. If non-conforming service is provided or a defect arises in a replacement part or product during the applicable warranty period, Apple will at its option, either (a) re-perform services to conform to their description (b) repair or replace the part or product, using parts or products that are new or equivalent to new in performance and reliability, or (c) refund the sums paid to Apple for service.

icwvx wrote:

So low possibility of botching the repair but also low possibility of getting a replacement (if botched) w/ an older iOS.

Have always stopped updating after 1 to 2 updates as these devices all run best on the iOS they were designed to run on.

Not to mention re-sale value. iPhones mint in the box with original (or close to it) iOS command a good price.

Apple's repair service doesn't consider collector's value or whether or not the customer wishes to maintain an older version of iOS. Any replacement device is likely to be reasonably new and loaded with the latest updated version of iOS. And personally I haven't found that an iPhone runs worse with newer versions of iOS. I've only found discontinued compatibility for older versions of apps. The big thing is usually that surfing the web gets really power hungry as newer websites throw the kitchen sink at the processor - especially with animated ads.

If you really need to absolutely keep it in at an old iOS build, then Apple can't guarantee it. Even if you get back the same device, they reserve the right to restore to factory settings, and the only way Apple does that is with the latest version of iOS. I wouldn't even guarantee that if they didn't restore to factory settings, that they might not just allow the latest iOS update as part of the service.

Legal - Retail Store Service - Apple

Apple understands that your data may be valuable to you. Data loss during service is always a possibility, and in some cases, data may be unrecoverable, erased, or reformatted during service. For this reason, it is your sole responsibility to back up all existing data, software, and/or programs from your product, and to decide whether to erase any such data from your product, prior to receiving service. Apple is not responsible for loss, recovery, or compromise of data, software or programs, or loss of use of your product or other equipment arising out of the services provided by Apple. You represent that your product does not contain any illegal files or data. 

Apple warranty and out of warranty replacements are almost always the exact same model, capacity and even color as the u it turned in. It will only rarely be a different model and then only if there are no identical service units available.

Apple repairs (parts and labor) are warrantied for a minimum of 90 days. So if the battery replacement had issues, yes they will replace your SE with an identical SE.

Slim chances and yes they would have a service replacement unit available.

If it has the latest update that would be a good thing as it would have the latest security updates.

Google voice works just fine with the very latest iOS release. I use it all the time (iPhone 13 pro running current iOS 15).