Good eye on the conversation, Ian
My comment is
(to Q1 - who does it ?) ; Not many.
(to Q2 - should boards allow it ?) ; definitely, where the board's intended use/ride style allows for valid alternate stances.
(Kombat/ST and Carve all being good examples of not only where it can work, but should be provided to make a crossover board more versatile - or "customiseable"- even if each owner sets to their personal preference and never moves from that.
So the problem with this is that no manufacturers, even *B, have screw inserts that won't wear out (as was pointed out above).
I concur that not all boards need easily, quickly, indefinitely (i.e., durable) changeable screw inserts, but it certainly would be nice if all mid-range / crossover boards had them.
Instead, my boards have multiplied like rabbits, and now I have one board for each sail...