I guess where OP sees the problem is that if two people are looking to book awards at a particular hotel but only person B intends on using a SUA, then if person A books the award room first, person B is screwed. But if person B books and applies SUA first, then everyone is happy. Hotel still had the same amount of award inventory in both cases.

Edit: actually, reversing the SUA violates both cases above and that makes sense from an inventory perspective