It does happen all the time in Australasia.
I am half way through a 2 month business trip covering Europe, and Asia and originally booked all my rooms on my account after I logged in.

When I then went through to check the amenities at these hotels on their websites, they showed a lower price.

I cancelled all the bookings, then phoned the Hyatt's Hotels directly in France Thailand and Indonesia. I then phoned Hyatt Reservations and comfirmed all the bookings, including any bonus offers that were available. I half expect there to be discrepancies when I finally get all the accounts, but that can wait.

I could be wrong but it appears if you want to take advantage of a bonus point offer or similar, and you press book on the promo, an enhanced price is shown. It is more than coincidence that on 3 bookings in a row, this was the case. Old adage of buyer beware, regards bkkrop