I always understood that it was height requirements that were an issue to enlistment and most were fit enough (barring usual issues like eyesight etc).
As a bit of a thread drift, we had a lad binned off a Chieftain driving course as he simply wasn‘t strong enough to lift the back decks. That was the story, anyway.
I have a couple of SMLEs with "B" bantam stocks fitted. These are 1/2" shorter than "short" and 1" shorter than "normal". Evenso, the rifle without bayonet fitted would only have been about eight or ten inches shorter than the bloke it was issued to.
Drill must have been, er, unusual, especially with bayonets fitted.