This wasn't my experience. I just completed a 2-night stay (booked with 50k CC points), and added a third (paid) night once I got to the hotel. I did e-mail the hotel in advance to have them input my HH number into the reservation, so it showed up in my Hilton account and they could see I was gold. At check-in he included the breakfast vouchers without me asking. The gold breakfast was served at Laguna, the same place as the buffet, and included a plate of 3-4 breakfast pastries, a fruit bowl (with good fruit, like fresh papaya and berries), juice and tea/coffee.

Interestingly, the rate to add a 3rd night at check-in was about $20 cheaper than what was available online.