Go have a look at some videos of finals at the World Championships or World Cups. Almost all the top shooters shooting with the rifle on the palm of the hand, with blocks varying to almost non-existent (Seonaid for example) to quite deep, depending on body proportions and position. Most have a relatively simple block. One that is height adjustable makes a lot of sense given variation in target heights at different ranges - easier to deal with at the front than adjusting the butt plate.