I’d say the more likely version of that scenario is not all the forks merging, but them all collaborating on a common base project from which they each can still produce their own spin.

I just measured my usual toilet and while the hole is more squarish than the round one in the picture, the 16.5 length is about right. I don’t have any problem. I’ve got average sized junk, and have maybe a slender to medium build.

Maybe weight, whether one is a ‘shower’ vs a ‘grower’, or some particular anatomical proportion play into it, I don’t know. Maybe how far back one sits is key. Maybe people vary in their butthole to junk measurement. But I don’t think this is as universal a problem as OP thinks. But, hey I’m all in favor of a longer toilet standard for those for whom it is.