Apple replaced my phone instead of battery replacement.

Anything can go wrong during a battery replacement. You just proved to everyone that it can.

They are right in saying "that's not how it works". If they had to give you a new or refurbished phone, then you come out ahead, in my view.

They should've asked if you backed it up prior to starting. I've never had an issue with my 6S Plus. If I were the one replacing your battery, I would refuse to do it unless you backed up your phone.

Apple should promulgate a rule for all of their stores not to even attempt to do any kind of repairs (including a battery replacement) on an iPhone unless the data has been backed up. Or better yet, give the customer a form with all sorts of "legalese" on it that basically states it's not their responsibility if data is lost. People have come in here and complained about it (you didn't and you accepted that responsibility) and blamed Apple. The experienced users on here spare no mercy in slamming these people left and right for not backing up their data.

I have 200GB of data on my iCloud, so data backups aren't an issue for me. Anything happens and I can just restore the backup off the cloud. Including repairs that are "fudged up", and they have to give me either a new or refurbished phone. People getting refurbished phones however is another story and won't be covered here.

When I had to send an Android off to the manufacturer for service, they emailed me the forms to fill out and on the form it said "Please back up your data before sending. We are not responsible for any data loss during the repair". The phone came back formatted (factory reset), but I did back it up. I'm certain Apple and other phone manufacturers tell you to do this.

You can also rebuild that house, and of course you learned a lesson. One that I or other users on here will not slam you for.

My dad never backed up his 6S+. He asked me to help him back it up before bringing it in for the battery service since it was recommended. So while it took way too long to load and install iTunes he just went to the Apple Store anyways.

If he had gotten a replacement iPhone I think he would have been extremely unhappy. A lot of people don’t seem to care until they can’t access the data any more.

As the OP posted, anything can go wrong. I might take advantage of that for my 6S Plus, but since it was bought in July of 2017, I'd probably end up doing it at the tail end of the "promotion". My 6S Plus is used only as a backup.

When I bought my 8 Plus, the first thing they asked me was "did you back up your data"? They might ask again if I take advantage of the replacement, but since I have an 8 Plus as well, they probably wont and I can just get the backup off iCloud anyways.

This is one of those things that people should care about. If something happens, at the most you lose 24 hours of texts and stuff. I have mine set to back up to iCloud when it's sleeping and plugged in.