That just made me more confused? In one post Savin says thickness is body fat, and then he likes a post which says tone is fitness and thickness is actually mass. And then he says it's the same as the TiTS system where 'bodybuilder' has an explicitly different definition.
I just default to my headcanon that Brint and Brienne actually have very high thickness due to all their gains and anything that says otherwise is a conspiracy.
First things first: all body metrics in companion stats are just stubs. Do not take them as real indicators.
Well, what about Brint, then yes he is a bodybuilder, but without drying. Like Gregor Clegane from Game of Thrones.