We adapt to the locks you have

A phone cannot open an unmodified hotel lock — card emulation is limited to ISO 14443-4 smart cards, most installed locks are MIFARE Classic or iCLASS underneath that, and they only open for data signed with site keys held inside the lock. So Atrium does not pretend to be a card. It owns the credential for the stay and hands it to whichever driver suits the estate. Check-in, folio and checkout revocation are identical in all four.