That’s why I am wondering why they couldn’t get the door open. When I was a F/A (80s and 90s), we were able to open the bathroom door from the outside and did so when we had to—children especially would lock themselves in and not figure out how to unlock the door. Were the occupants of the bathroom holding the lever so the F/As couldn’t move the latch? Or have the airlines become so PC that they are only allowed to knock politely and ask, “pretty please”?
I don't know, but not having a "deadman" switch of some kind seems fraught with downside potential.