^ I'd imagine the easiest method would be to give out paper vouchers at check in (although not sure how that will work with their push into mobile checkin and keyless entry), but even with that, unless they are expecting a drastic decrease in the number of guests getting the free breakfast, I don't see how the staff would be able to police it. As it is, my experience with HP is that the staff have trouble keeping up with just having clean plates, glasses and flatware stocked.
And the staff are also dealing with customers checking out and other stuff during breakfast time. There isn’t a lot of extra staff resources at Hyatt Places to make policing the breakfast situation easy. Especially at properties where a room may be used by 1-4 people (despite the guest count entered into the booking) and people may come and go a few times into the breakfast area for one reason or another.
It will be interesting to see what percentage of people are upsold breakfast at check-in and what price they offer for it.