I like to use FMs fairly heavily in battles, with my main army usually including at least 4 FMs. For most factions (but of course not all) this comprises a fair slice of my heavy cavalry section of the stack. I use them as you'd expect heavy cavalry to be used, with flanking charges to break the enemy line mostly.

I've always presumed that using FMs this way would lead to them acquiring such martial traits and ancillaries that you might expect from a guy who really gets involved in the nitty gritty of killing other dudes. Things like bodyguards and spear carriers etc.

But is it so? Does it actually matter what FMs do in the battle? Or is being involved (ie present) in the battle enough for the game to assign that chance of getting a trait/ancillary, regardless of what that FM actually does during the battle?