I'm not sure, as I have not tried this myself. I've either departed non-Schengen, or else arrived non-Schengen or connected to Schengen the next morning.

I should imagine that if you arrive and depart Schengen the Marechaussee will let you through on the basis that there is no terminal hotel on the Schengen side; but when your starting point is AMS, they might argue that there are plenty of hotels landside.

Perhaps you should call the Mercure and ask, they ought to know. I shall PM you their number.

Johan