So - why have they done this promo?
Some things come to mind:
1) They wanted to give something to their elites, and clearly distinguish Diamonds from Golds here. One of the common complaints by Diamonds is the lack of recognition over Golds.
2) However, Golds also got a Top-Deal, even if tied to stays. A fast-track to Diamond for some, specifically fast-tracks for requalification of former Diamonds may point to the fact, that Hilton has seen people actually voting with their feet, leaving the programme?!