If you are asking about the gift cards, I would not expect them to be accepted:
...that does not tell us if an American Express Business Platinum charge made at a SLH property would trigger the credit.
Nope, asking about using the ABPs directly. I'm curious because I know that SLH properties can code under a very different name, and while it is a HH hotel, I could imagine Amex not detecting it properly. Reason why I was looking for DPs.