I've learned to not trust Apple support on anything. My daughter's Watch screen cracked and we sent it in for a replacement. To setup the replacement though, they requried that she unpair then repair the watch then-and-there. They said she wouldn't lose any data, that it just disconnected it from the phone.

Nope, unpairing is a complete reset apparently. And Apple Support was apparently not trained to know that not everything syncs in the backup. She lost all her voice memos, which she uses for class notes, and probably other app data as well.