Neither of you really have a conclusion. Your modality is overly-reductionist. His is overly broad. In both cases it's impossible to reliably measure. What had ought to reasonably be concluded, then, is that we're entirely ignorant as the the capacities of an individual. From that agnosticism, then, we can build a framework of expectations. And that is entirely elective - if you want to say that nobody is exceptional, you'll seek to reinforce that. If one elects to search in every individual for some special capacity, that's what they'll find. I don't know about you, but between those two framings I'd prefer the latter.

Then there's the objectivist train wherein no expectations are allowed, one must duly profess their ignorance and make baseless measurements in estimation and comment on the distribution of faculties per individual and the degree of resolution to which these measurements are allowed to take place - and it isn't to the degree which any great conclusions can be drawn, I assure you. There is no means by which you can splay out a person's whole and examine them. Time spent with one or two is time spent neglecting some other specimen. Not to mention the interference added by environment. And even in the best of cases that time spent may only be revelatory of some minute fraction of the whole, where again only some shallow conclusions may be drawn and they're only conclusive insofar as the observer has decided they are at some point in the context of time and space within their ever-evolvong system because there's hardly a tape measure suited to the infinite degrees of freedom that exist in the world.