Originally Posted by
TouchandFeel
That "weird flex" isn't weird at all, it's simply part of the natural wind up and bracing for swinging a large heavy object in a wide arc from over your head or shoulder.
If you look at the way a sledgehammer or other such object is used in real life, when used properly, it is fairly similar. You bring it up over your head or shoulder with your hands spaced apart to distribute the weight, helping to minimize the effort of lifting, and providing better control as you start your swing. Then as you swing you bring your hands together towards the bottom part of the handle to create a singular fulcrum near a point where you create the longest radius between fulcrum and edge of the arc, thus maximizing the size of the arc and distance traveled which allows for more force and acceleration to occur before you land the strike with the sledgehammer, axe, sword, whatever.
It's not "weird" it's the naturally occurring result of when biomechanics and physics meet. The Bloodspiller animation obviously takes a bit of liberties and fancies up everything to make it look cool, what with the extra full rotation for added force or something I guess, but overall it actually makes a decent amount of sense.