Well, the old researcher and joker in me wants to say the study really only shows that those who know how to punch better tend to punch better which is not exactly a revolutionary idea...
Doing it "right" makes for a more efficient movement. Hence more "power" when needed as compared to someone who can't get the movement coordinated right. And any good striker punches with more than just their arm... A good strike is actually quite a complex movement.
But yeah, there are some interesting implications here...
I think their findings would be consistent with any physical activity that someones does long enough. Carpenters don't swing their hammers the same way they did the first day they picked one up. You learn to use the body more efficiently and that includes dropping muscle usage that isn't needed for the task. Similar in some ways to things that are talked about here, but far more simplistic.