being a platinum member doesn't require much with 5 stays and hyatt gp is one of the most generous on that front with free wifi, 2pm late check-out, 15% bonus on points and an elite rate which is 20% off rack. This is far more than what other chains offer for their entry level elite tier. A legitimate extra bed charge is not unreasonable.
I am even charged this as a courtesy card holder at GH NYC, Andaz west hollywood etc etc. It is a very reasonable fee, and being platinum does not really entitle you to a waiver, nor should you expect it.