Whatdayamean? That a supposed peak human with a 20 STR is only 5 ability modifier points better than a supposed average 10 STR person with +0 (resulting in merely a +25% bonus in capability)... isn't truly representative of the difference in human build and action? Get outta town!
And to think... that supposed peak human with the 20 STR can attempt basic DC 10 STR checks and fail 20% of the time by rolling 1s, 2,s 3,s and 4s. Whereas even humans with a STR of 3 (-4) can still sometimes complete a DC 15 task by rolling a Nat 20.
It's almost like game mechanics don't actually represent anything real or concrete in the fiction and are there merely to give us some numbers to play the board game with! Whodathunkit!