Huh. Well, I'm 48 years old and started riding dirtbikes when I was 6. So I've worked on my fair share of vintage Japanese motorcycles and stripped out my fair share of float bowl screws (and got good with the hand-held impact driver), but I was under the impression it was more the soft metals than the screwdriver heads.
I believe I have these in my current sets, but don't have any vintage Japanese stuff around to test that theory.
Learn something every day!