So, ignoring everything else that has been said because a lot of people are missing the point, I do want to purely focus on your conclusion. This is how every stat works for almost every spec, stats multiply each other so the vast majority of the time you're going to be looking for relatively balanced stats. You'll index into one or two a bit more than the others but you're not often going to benefit from dumping everything into a single stat nor neglecting a stat entirely.
Following from that, I think you're focusing on versatility here too much, this will happen with any stat. You also can't really call it a cap because it's not a set in stone number, it's totally dependent on your distribution of stats.