There shouldn't be "Adventurer Humans" and "Regular Humans". That'd just be silly.
The fundamental premises of heroic ability scores in most editions of D&D rests on the idea that there should be "Adventurer [Insert Race Here]" and "Regular [Insert Race Here]" with vastly different stats.
If you want to call that "silly" it's your prerogative, I guess.
Humans are Humans are Humans.
They call it the "Heroic Array" and "Human Average" for a reason. The human average for any given stat is 10. Your typical peasant has a 10 in any given stat. 10-10-10-10-10-10 if the default for an unexceptional NPC Human.
The typical "Adventurer Human" is running with a base of 15-14-13-12-10-8 nowhere near "Humans are Humans are Humans." The same can be said for "Elves are Elves are Elves" and "Dwarves are Dwarves are Dwarves." When you get right down to it the 15-14-13-12-10-8 vs. 10x6 is such a huge gulf that the adventurer getting to specialize at +1 to a stat or two is negligible.
What kind of horrible violation of verisimilitude is inflicted by a human adventurer being
15,14,13,12,10,8 +1 to any 2 vs. human peasant being 10,10,10,10,10,10 while an elf adventurer is 15,14,13,12,10,8 +1 to Dex vs. elf peasant being 10,10,11,10,10,10? If nothing else this reflects that while the average elf may be more graceful and swift than the average human a human that grows up to be a hero is typically just a small cut above his elf counter-part in something other than Dexterity, but then we start factoring en Keen Senses, Free Spirit, etc and it all comes out in the wash.
The game already clearly bears out that "Adventurer Human" and "Regular Human" are playing in two completely different ballparks when it comes to stats, so I think you're arguing a moot point.
- Marty Lund