When I check in as various Marriotts, sometimes they swipe my card (it seems like a norm in Hong Kong because other hotels do too), and sometimes they don't.

So I always get my CC ready at check-in. I don't know why they have to swipe my CC even though I have already got 1 in my profile.

It's not a problem to swap with paying with GC, I normally ask for it at check-in so they have time to sort out the payment (I'm not based in the US where GC is commonly used).