First player batted .275 in like 1890. Sub 4 happened in 1954.
That's your first big clue that sub 4 is tougher. It really isn't even close... and
zillions more try running than ever play baseball.
How many around the world would hit .275 if more than a few countries played the game? The correct answer is probably several thousand or more per year. 20 guys from each country on earth would mean 4000 .275 hitters per year.
Maybe the average person would look like a fool trying to hit a 92 mph curveball or a 65 mph knuckleball but then the average person on earth also can't run 15mph for even a fraction of a second let approach the 18 - 19 mph peak running speed required to have a decent chance at sub 4.
Moreover, given global obesity rates, fewer and fewer will be running these times in the future, even if they hold all track meets indoors at UW, BU, Birmingham or Dusseldorf.
Now maybe if you took the mound back to 16" and the tracks back to cinder, and weight of spikes back to 8oz and the indoor tracks to unbanked and 11 laps per mile (and then outlawed pacesetters for good measure) we could get to the bottom of this.