While that certainly explains why they might use a microcontroller, it's certainly not necessary. The lock can be connected to a simple switch used for signalling occupancy, same as any security or commercial fire protection system. Auto-closing and auto-opening are akin to an automatic door, which operates just fine as a regular door, but has a fairly dumb motor attached for accessibility. Perhaps the microcontroller solution ended up being cheaper - but based on this (particularly going to out of order after such a trivial "hack"), the mechanical solution is far more robust, because at worst you can still operate the door manually.
They also auto-close the toilet door when not in use to keep smells away.
And the main reason: Doors aren't really wheelchair friendly - many wheelchair users aren't strong or agile enough to move a door.
With those 3 things to deal with, it's pretty hard to design a mechanical door system that can meet everyone's requirements.
Having said that, the UI could certainly be better. I would personally have had the 'close' button require to be held down the whole time the door is closing. If you release the button early, the door opens again. Only when it is fully closed will it then stay closed and 'locked'. No need for an actual mechanical lock, but there should be a big red padlock light that comes on.