Photos Counts Different on New Phone

I got a new iPhone 13 Pro to upgrade from my 12 Pro and I have fewer photos on the new phone. I use iCloud for Photos. This did not happen to me last year when setting up the iPhone 12. At that time, the counts matched across the devices because I checked it then.

For the iPhone 13, I set up the new phone using the restore from iCloud backup. I ensured that iCloud (and the Photos app) showed as up to date before starting the restore on the new phone.

I immediately noticed that the photos count in the new phone's library was a tiny bit lower than the count on the old phone.

I have two Macs. One is my daily working computer and the second I keep just so I can have an external HD and have it download all photos to the local disk. Both Macs also had slightly different counts from the old phone, one matched the new phone, and one didn't. It didn't occur to me to look at iCloud.com at first, so I am not sure how that number compared when I first setup the new phone.

Eventually, I started tracking iCloud.com too and it has fewer photos than the old phone. It has a smaller gap, but still less than either Mac.

For perspective, I have a pretty big library and so I gave everything days to see if it synced up. You could argue that what difference does 66 pictures and 10 videos make relative to the overall size, but it still undermines my trust in the whole experience. I don't like the idea of loosing pictures.

• Old phone stayed plugged in and connected to Wifi for several days to see if things synced up.
• I have checked it periodically, and at any given moment, each device stays the same number of photos off from each other, but they all still get updated with new photos.
• All devices show that they have synced on any given day and throughout the day (like says “Update Just Now” etc at bottom of library)
• I tried taking a photo on the old phone to see if it spurred some sync process, and that new photo showed up everywhere but didn't help with the count reconciliation.
• Eventually the two Macs, iCloud.com and the new phone had the same count, but all less than the old phone.
• Just in the past day or so after seeing the new phone has more photos than the Mac but still less than the old phone. Ever since that one shift, they have stayed the same number off of each other.
• Tried the smart photo album of “could not upload” on the Main Mac and Photo Mac, both are empty (which sort of makes sense based on the computers being behind the phone, but one computer is ahead of the other one)
• Ensured all devices had sufficient disk space to allow for syncing (I have noticed that syncing can stall when the local disk gets close to full)
• I tried to plug the old phone into the Mac that stores all of the photos locally to see if it saw a bunch of photos that weren't in the Mac's library. It shows like 18 pictures + videos (which doesn't even cover the gap in counts). It shows that they are previously imported. I actually searched the Mac's library for those photos and they were actually already in there. So this step didn't identify any photos that had failed to sync.
• Checked that my iCloud subscription shows plenty of available disk space.
• All devices restarted multiple times
• All devices on latest versions of software macOS 12.3.1 and iOS 15.4.1

Here's the counts (first number is photos, second is videos):

• Old Phone (iPhone 12 Pro): 173,028 + 15,728 - setup to optimize disk space
• Main Mac: 172,970 + 15,719 - setup to optimize disk space
• Photo Mac: 172,962 + 15,718 - setup to store all photos locally
• New Phone (iPhone 13 Pro): 173,006 + 15,724 - setup from iCloud backup of old phone
• iCloud.com: 172,961 + 15,718