Hi,
Yep same system on my Mazda 6 and 3, never had an issue, but they are a few years older.
Perhaps a bad batch, as you say. Or a change in quality!!
The servo seems to work both ways to either lock the steering or unlock, may be spring loaded, but unlikely as this would create a risk of locking the steering should the servo fail.
Looking at the wiring diagram it seems the switch in the door has two connections, one to the body control unit and one to the start stop unit. The latter seems to have no other function than to tell the start stop unit that the door has been opened so it can lock the steering.
As long as the steering lock servo is in the unlocked position the car will start. Reguardless of the door position.
I will try to disconnect the pin when it is in the unlocked position and see what happens! It might not lock the car, but cant see why it wouldn’t as the door has to be opened first to activate the steering lock so the door switch must be normally open circuit when the door is closed!