The watch backs up to the phone.I had issues with this. I wanted to unpair my new s4 watch from my XS phone, then pair it with my X (since I was gonna return the XS). The only info I could find said that watch backups are done automatically when unpairing, and when backing up a phone. Since my phone was already backed up that afternoon, I proceeded to unpair my watch from the XS (certainly both backup methods were covered in this case, right?). Then I paired it do the X, and tried to restore from backup... but there was nothing to be found. The only backup available was a s0 backup from November 2017. Wtf?
I tried multiple times and could never get it to work. Makes no sense since it was the exact same watch, just moving to a different phone. Very annoying. I wish it would just let you see it like any other device.
However, whenever I’d get a new phone, and restore from backups, I’ve always been able to restore my watch as well. I guess the backups are linked to the phone backups, rather than individually? I’m not really sure, but it was very frustrating.