Doubt on Inverted W

As far as I see the websites written by instructors and researchers, so-called 'inverted W' has seemed to be considered poor mechanics that could cause pitching arm injuries.

However, as many players or on-site instructors may well know, this kind of form in which both elbows up, leaving those hands down at the same time could never be seen in the mechanics of lower level players. Many of them would show the ones such as pie-throwing arm and javelin-throwing arm. They could never make inverted W.

So I think there are 'good inverted W' and 'bad inverted W', and good inverted W should rather be said as an ideal form in the pitching mechanics. Craig Kimbrel's pitching mechanics is one of the good examples for it.

Then, what is the difference between the good and bad one?  Good inverted W is that in which both elbows are pulled up at the same time, interlocking with the lower half's movement and harnessing the power of it. On the other hand, Bad inverted W is that in which both elbows are pulled up forcibly by exclusively the power of shoulder muscles and there is no interlocking with the lower half.


Note: Craig Kimbrel has a problem of short stride and it can possibly cause some kinds of pitching arm disease. Yet that should not have something to do with his 'inverted W'.