I used these yesterday to book an AirBnb in RAR. Card loaded just fine but they count it as an immediate credit rather than a form of payment. Example:
Booked house $800
I wanted to pay half now and half the week before arrival so I was expecting to use $400 now and the rest would sit there until Feb when I booked the house. But they took $500 off the $800 right away with a balance due of $300. Then they wanted half that as deposit so I had to put another $150 on the credit card leaving only a balance of $150 due. This must be paid by credit card as a future gift card would only auto-deduct from a future booking.
So lesson learned is to load the exact amount of the rental on the card if there is another points bonus like this again.
Hopefully this doesn't mess up my future 10,000 spend x 4 week bonuses.