If the door has no means of mechanical egress, for example, a maglock, then it is required to have a second form of egress that cuts power to the maglock, such as a normally-closed exit button. Maglocks naturally unlock when losing power. Electric strikes and locksets can be set up fail-safe or fail-secure.

Not the commenter you replied to, but these kinds of systems are usually “fail open”: if there is unexpected loss of power (including the locking mechanism connection to the controller being interrupted), the door is released/unlocked, and can be opened manually by users.

Some more complex systems will have specific doors automatically shut in the event of a fire to try and keep it contained, depending on local regulations. These doors can still be manually re-opened, but they will not “catch” or latch open until the system fault is resolved

Edit: add clarity