In my opinion yes you should not be charged for something that did not exist when you booked your reservations. To me its akin to baggage fees on airlines. When they first implemented that fee they didn't retroactively charge people who booked a flight before the fee was instituted. I think the same should apply here.

Note - I have no clue what Hyatt's position is here - you may want to PM their account here to get clarification.