It may be that they have no choice since it's their biggest source of customers. I spoke to a hotel receptionist before and she said the order of upgrades was:

It may be that they have no choice since it's their biggest source of customers. I spoke to a hotel receptionist before and she said the order of upgrades was: booked direct, booking.com, Expedia and all the rest after. The hotel couldn't afford to piss off booking as they would suffer a lot in occupancy, the other platforms couldn't match. I think it's worth giving the feedback to the restaurant direct and see if they can fix it. It's always a delicate balance depending on time and the app may penalize them.