I still haven't seen the gift card $50 credit but something interesting happened...

I used my DH's amex card to buy a $100 gift card. Then used the gift card to book an AirBnb place and used my amex card for the remaining total. Today a $50 credit posted to my account despite the fact that I used a gift card to book the property. The terms clearly state that the credit won't be applied if a gift card is used.

So if and when I finally get the gift card $50 credit, then I will have received $100 off my booking.