Looks like no matter which address I assign the credit card to, it passes the address that is linked to the credit card. I changed it several times, and pp switched to the newly assigned, credit-card linked address each time.
Also, once I swapped the cc off of one address and then tried to change to that swapped-off address that no longer had a cc assigned to it, then pp produced a new page during my test checkout to then add a new cc, meaning that swapped-off address did not have a card assigned to it even though it might be a confirmed address.