Whether you're of the opinion that the rules stifle innovation or not, the line has to be drawn somewhere. Otherwise, this course of development would have probably had a parallel evolutionary track to the outboards, and turned our traditional ski boats into inboard versions of a Mod VP. That in itself would not have been a bad thing, but it would have made a lot of existing equipment obsolete, thus decimating participation.
A similar controversy exists today among ski boat circle racers regarding Vilwock's turn fin. I think it should be outlawed, not because it's dangerous (the jury's still out on that), but because if it works too well, everyone will have to do it to stay competitive. The design will evolve too far away from what a "ski boat" is supposed to be. On the other hand, one could argue that capsules have already done that, and once the mandate axe falls, who cares? Let 'em go.