#21
It is neither old nor silly, it is the FIDE rule: 4 pawns fit on a square.
Mind you I have yet to see a set where 4 pawns will completely fit in one square (even in sets/boards actually used in major tournaments and WC matches) and I think the pawns would look tiny on a board if they could fit 4 to a square. I think the operative word here is "should" as opposed to must. So while "silly" may be overstated a bit, "old" and "unobserved" are accurate words.
#21
It is neither old nor silly, it is the FIDE rule: 4 pawns fit on a square.