I don't believe the wording means arithmetic average.
It's more akin to the reasonable person test in law. Meaning, a reasonably well trained pilot that is not considered significantly more expert than those around him or her.
Just a side note from a law nerd. 'Reasonable person' doesn't mean 'typical' or 'ordinary' person, it means 'person who is amenable to reasoned argument.'
Suppose you make a proposition to a person and they reject it based on some fallacious argument. You, an intellectual, kindly point out the fallacy in their objection. A reasonable person is one who takes this in and reconsiders your proposition. An unreasonable person is someone who doubles down and either offers different but equally fallacious arguments (if they just hate your proposition and are looking for an excuse to reject it, but wish to conceal that) or refuses to acknowledge their original fallacy (due to embarrassment, stupidity, or perversity).
It's more akin to the reasonable person test in law. Meaning, a reasonably well trained pilot that is not considered significantly more expert than those around him or her.