My guess is that the airbag design and position were an afterthought for the existing models. It needed to fit in the glovebox space. Period. No one considered that little screw. I assume when they designed the later models, they put in gloveboxes and put the airbag more out of the way.
It actually isn't a tough job to get the airbag out. One screw, and you're good. Just don't jimmy that plug on the back. One of the easier jobs I have done. Try changing that serpentine belt on a warm engine!
If that job can be done without removing the airbag, my tech didn't know it. And those guys don't take the long way unless they have to.
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K