"First, it is open to every GP member and doesn't require registration (unlike UA 1,500 miles, which, BTW, posted w/o problem). So why does it rely upon property input?"

The large majority of guests don't know about the bonuses. So, Hyatt saves a lot of points and money by not doing it automatically. Ask any desk clerk who has been around 5-10 years what percent of guests ask for a particular G1, G2, or G3 bonus and the answers you get will vary from 5% to 40%. A lot of guests don't even have a Gold passport account! And during Faster Free Night promos, a lot of guests don't pay with a MasterCard.