[Torin]

You actually have to check spell casting encumbrance to know, its higher than normal encumbrance.
6 is too low, i dont have the game here but checking edis db`s excel i dont see any starting commander with 6. But i checked 2 early era nations:

EA Ermor - Centurion is sc enc 7 , wich is very acceptable and gets you 14 smites before faints
EA Acrocephale - Myrmidon champion is sc enc 17 - only 5 smites before faints

in edis db its labeled enc2

so sometimes is better to prophetize your commander, sure.