...do I need to simply unpair from current phone and pair with a new one or does every device change force me to reset the watch.
Yep. Apple needs to rewrite the entire backup architecture and bring it forward from the dark ages. You lost all of your Health data too, if that was important to you.I've just had the problem of moving from my 6 Plus to 6S Plus. Due to another issue, I the new phone has been setup as new. This means that there isn't a backup from the watch and I've lost all my data.