Well, actually no, kitefoil pocket boards makes sense, small and fun and you can still start because you have the kite powerspike - or at least drag yourself ashore looping the kite.
With small wingfoil boards, when too small, it gives a very small advantage, for many not noticeable if not freestyle.
So it seems that the early "frontrunners" have gone down in size, a lot, to test the limits, and then up again.
So 15-20 litre under your weight, yes, but smaller than that hardly used now.
And when riding in say 14 knots, and the wind drops to 7 knots, it is so much easier to get ashore if board is not too small.
Not a safety concern, just bugger to have to slog ashore...
Of course location specific indeed (wind consistency at least), but many around here goes with either one board now, not too small - or two boards, one sinker not supersmall, and one for light wind closer to your own weight in volume.
Because of the initial "desire" to go small, many other "one board riders" have done the same, and regretted.
A bit like the early windsurf days, where sinker shortboards should be as small as possible (we have all been there in the start 80s, I was one of the worst going crazy small) - to try the limits and for the fun of it.
This changed, and size went up again, and have stayed ever since at a reasonable length, not too big nor crazy small as they worked so much better in all respects.
I assume the wingfoil evolution in different locations are very different, so some regions have gone past this and more settled now.
But the other thing which happens, is you start learning winging with a big board, maybe not really big, but a tad bigger than good when experienced.
Then when you buy a new smaller board, you dont buy one just a bit smaller, but a lot smaller (many do), so easy to overdo it for many.
This thread actually just a reflection on what I see and hear around here from many wingfoilers
Knowing it wont make any difference, as everyone probably have to learn personally, where too small is too small, and when they are too big - for their personal liking