So let me break this down to see if I got it. Reasons not to train the bridge men:
1) Sadeas and his men are cremholes
2) if he did train them well enough and they could outrun parshendi arrows then the soldiers would instead be fired upon, which Sadeas obviously doesn’t want.
3) even with proper training and leadership Kaladins team at bridge 4 would have died several times over if not for the fact that he Was a surgebinder, which of course doesn’t fit the general description of most people.
that seem right?