> e.g. By definition the 99.9th percentile person cannot live a 99.999th percentile life, if they did they would in fact be that amazing.

This seems far too deterministic and I think is contrary to what you're replying to.

It sounds more like a 99.999th percentile person[0] that constantly reaches too far too early, before being prepared, will not have a 99.999th percentile life. A 99th percentile person who, on the other hand, does not constantly fail due to over-reach, can easily end up accomplishing more. (And there are many other things that might hold them back too - they might get hit by a car while crossing the street.)

[0] in whatever measurement of "capability" you have in mind

Significant part of what separates 99.9th (or even 90th) from 99.999th percentile is ego management.

In particular IQ is not associated with better life outcomes after you have "enough", and that "enough" isn't Mensa level.

Can we invoke a version of 80-20 rule here, that 0.1% people will easily capture success of 80% while subsequent marginal capture takes increasingly more investment and luck?

John Quincy Adams was arguably such a 99.999th percentile person though.