The classes are divided by jump heights in order to make the competition equal between the different size of dogs. (gsdcw.com)
In these zones, you can set your health, weapons, equipment, shields, damage and even increase jump height, movement speed, etc.. (thatvideogameblog.com)
I encountered occasions where the character's slightly lower jump height left critical platforms slightly out of reach, which was likely by design but which feels very frustrating while you are playing. (gamecrate.com)