I've decided to give it a go. I've made a (cancellable) booking and separately wrote to the hotel to confirm that perks do apply. The app correctly shows expected earnings at least. If nothing disappointing comes back I'll update everyone after my stay next month.

PS: and yes, definitely new to all.com as Goldorak say! When I first looked to book last week I'm certain it wasn't showing on the list of options and I doubt it was full as booking now it shows availability in at least three categories on my dates.