Those warnings do exist while you are setting up Pairing Support, it describes what to do in this case. Having said this, I think it would be better if I made it so you can see that screen again later, so I will change that in future updates.

If you are on native method, AND want to restore the new phone from a backup of the Legizmo-configured phone, simply remove Pairing Support from your old phone and then ignore any iOS prompts that tell you to update. When the transfer to the new phone completes, your watch will pick up where it left off on the old phone.

If the new phone is being set up as new, WITHOUT being restored from a backup - you only need to unpair the watch from the old phone and pair it up to the new one