On the two occasions I did use the App I got that notification both times, hours ahead of my stated arrival time.

That said this is one of my pet peeves. Unless the hotel has me in an upgraded room and I desperately want to keep this, not having a room available past published checkout time is a no-no in my eyes. I think that some form of compensation is definitely in order for this shortcoming of the hotel.

Greetings - Dirk