This is my theory of how the change in artist has affected the art.

Bak (the first painter of the style) is seen to have struggled Amarna, as is seen through "Sculptor's Model with Two Royal Portraits", the limestone block seems to depict two different figures (this was initially though to be true) but further analysis shows that both are struggles to depict Akhenaton in his preferred style. Also in an naos containing a sculpture of Bak and his wife, an inscription states that the Pharaoh himself taught Bak the craft; and as we are to assume that the Pharaoh wasn't an artistic genius that he wasn't the best person to be teaching Bak. The limestone slab was one of the first pieces created and conveys his struggles >> which may I comment didn't evolve much :)