It amazes me when someone makes improvements to a job as old as splitting wood. Millions (billions?) of people have been doing it for thousands of years, and there's still room for improvement.
Chopping firewood takes up so much labor, that there have always been specialised tools, there is no such thing as a "normal axe" - an axe for felling trees is different than an axe for splitting firewood, there are differences in the shape, width and weight of the axe head and you wouldn't want use one for other if you're doing it more than once a year; and a carpenter would use a different type of axe(s) than those.
And that's not a modern invention, it goes back for centuries. I'd guess that even stone age flint tools have been specialized in similar ways.
True. It's also worth nothing that axes intended as weapons are also very specialized. Indeed, there are multiple types, depending on just how you want to kill people with your axe.
This isn't actually a new improvement, just a 'hardware' implementation of a really old technique. You can get the twisting action with any normal axe, even if you're a barefoot girl:
I found it entertaining, mostly for the interesting use of language.
"Once in a while he found new axes at the hardware store. They were proclaimed to give greater striking power and strength through added weight and a variety of shenanigans to the sides of the blade."
I'm guess that it's less useful if you're chopping against the grain or if you want precision.