The player's first-person hand animation appears much lower since 15w34a, a 1.9 snapshot.

Prior to this snapshot, the hand animation would nearly reach the crosshair, making it feel like you're directly punching the block or mob in focus. Since 15w34a, actions like digging, mining or attacking at faster speeds can cause your hand to be barely visible during the animation (see video B).

This change has not been documented anywhere, which is why I believe it might have been unintentional. 

Below is a video comparing the difference, showcasing versions 15w33c, 15w34a and 1.21.4.