[munchbunny]

if 100% of the engineers are operating at say Staff Engineer level, do they all end up with that title? Or does the Staff Engineer title really come down to some sort of percentile in a stack ranking?

If you actually have 100% of engineers operating at the Staff Engineer level, then it is what it is. However, the only case I can think of when that should ever be true is when you can count your developers on one hand. Once you grow any bigger, it's just not an efficient use of your money or the engineers' time to have that much experience concentration (as opposed to talent concentration, since more junior people can be talented too).