No. The federal law was changed to eliminate the gray areas. It is now very simple. It was stated back in post #6 so I won't repeat it. In the event that you do imagine it to be gray area, you can ask an ethics consultant.

Under the old law there were many gray areas that led to constant disputes over what the traveler could and could not keep. For example, meals on the airplane, free breakfast at the hotel, meal vouchers, discount coupons, and so forth. It used to be a nightmare. Do you need to subtract the airline meal from your per diem allowance? That kind of question.

The current law refers to "all" promotional benefits from travel service providers. We have to assume that "all" includes cash. One exception is the involuntary bump because that is defined in a way that makes it not a promotional benefit.