Interested because same situation arose in Zurich. Late arrival 630 am departure next day. Passport control announced as closing at midnight. In this case I collected bag, exited landside and returned airside late with no questions. Spent a pleasant evening with a few others doing work that I needed to catch up on and a few winks and off I went. No facilities other than vending machines, bathrooms and water fountains. Same thing recently as well but stayed airside Zurich...again stayed up and worked. Non issue taking room but sometimes it does not make sense, And yes T4 premier inn is my go to place when I decide otherwise. No security patrolled and the only others were the floor cleaners who did a few sweeps with their machines. Very thoughtful that lights were dimmed as well for around 3 or 4 hours. Thanks for input of all replies.

For completeness sake...there are rooms and beds without rooms airside for purchase or you can exit and choose the new pod hotel which prices at around $100 CAD for the night and even has a hot tub if you do not mind sleeping in what are essentially closed off bunk beds and listening to persons coming and going at all hours with doors closing etc. I likely slept better in the terminal for the hours I managed.