IME, you can switch a revenue stay rewards number no problem AFTER you check in with the Ambassador member to get all the benefits however that cannot be done (or at least I haven’t been able to get it done) for an Ambassador guest-made reward stay and switching at check out to someone else to get qualifying credit. Having said that, if the gold made the award reservation, and the ambassador shows up with the gold, then it’s up to the hotel to grant benefits.