I'm sorry, but that's just bullshit. The rule was implemented as a patch in to deal with the fact that Strength is the most efficient stat in 2e. Everyone wanted to max out their strength score and Gygax didn't want everyone coming to the table with near-identical stat blocks. So, for one value - 18 - in one stat - strength - he created a secondary rule that stratified characters that much further.

RPGs are games, not art, and I don't give myself airs.

This is also nth-levels of bullshit.