Thank you so much benveniste! What you say seems to be based on real experience.
Yes, I guess I was pushing the lens against the metering tab; there was a springy feeling at first. Luckily, the tab shows no signs of damage as far as I can tell. (Can't I post pictures here, because of my "basic" account?) And I certainly noticed nothing odd upon removing the lens.
I have no easy access to AI lenses, but I'll try to find one and try it later.