Why no, it’s not supposed to be possible. I’m pretty sure that I couldn’t have done it by myself, but Apple helped make it happen.
Last week, I bought an iphone 13 mini to replace my 8 and an ipad air 5 (love the ipad, the phone’s ok). I also have a watch 4. I backed up the 8 to imazing, and then restored that backup to the 13m. In the process of setting up the 13m, it asked if I wanted to pair the watch with the new phone, and I said, sure, get it over with. Checked to see that the data was indeed going to the new phone and not the old one.
Didn’t take long to find out that the watch battery was having a hard time of it, going from ~36 to 22 hours of life. Did the usual rebootings and such but no joy. tabled it for the future since ipads are more fun. Then yesterday I tried to answer a phone call on the watch. No sound in or out, had to call back on the phone. Finally looked at the watch app on the old phone. Bingo, it was still paired to the old phone. I had to unpair it from both phones and then pair to the new one, but it’s now happy again and I can go back to the nifty new ipad, on which goodreader can handle a 1500 page heavily illustrated textbook with aplomb, and which will happily let me use a 256GB flash drive.
I’m surprised that there wasn’t more havoc from the snarl, but annoyed that it happened at all. I haven’t found any similar tales with a quick ducking.