I called the Conrad to ask, and this is what they said.

1) Must book directly on Hilton site (obviously)
2) Gold or Diamonds receive the same benefit, comprising $25 of food and beverage credit per person, up to $50 per room per day
3) May be applied towards room service or Estuary (unclear if it can also be applied to the rooftop bar/dining)

Very generous! And Estuary is phenomenal. And it stacks with Sakura Club access because I received it when I was staying in a SC room.