This is explicitly in the T&Cs. Not sure if it is for the new promo.
Hilton is all about incentivizing stays over nights though.
The only way I can get diamond is to have 30 stays. This is quite easy for me, yet 60 nights would be quite difficult. Sure, I'd prefer not to move hotel unnecessarily but that's how the program works. Once I am sure I'll go over 30 stays then I may consider booking more than one night in the same property
Yep, you are the same as myself, I scrape through with around 35 stays a year usually one night stays as I’m in the music business and I tour, 60 nights is out of reach for me too.