The whole point of a flat surface is that you have a higher surface area between the ball and the mallet (leading to straighter shots etc).
But, the ball isn't flat. It will deform on impact, so you will have a certain flat surface (not just a point), but around the edge of that flat surface you'll get a curve.
By having it concave it should increase that surface area, and therefore lead to even straighter shots.
But if you go too far you start to have a ring of impact, and not a central point (an uncapped mallet is effectively a massively concave one).
Either way, I don't think my milk is any more concave than it was at the start (which it was).
Well, I don't think that's for sure.
The whole point of a flat surface is that you have a higher surface area between the ball and the mallet (leading to straighter shots etc).
But, the ball isn't flat. It will deform on impact, so you will have a certain flat surface (not just a point), but around the edge of that flat surface you'll get a curve.
By having it concave it should increase that surface area, and therefore lead to even straighter shots.
But if you go too far you start to have a ring of impact, and not a central point (an uncapped mallet is effectively a massively concave one).
Either way, I don't think my milk is any more concave than it was at the start (which it was).