It's the sort of culture that would expect, "Here lies our lord, cut to pieces, out best man in the dust. If anyone thinks of leaving this battle, he can howl forever," except that our hero has the slight complication that they kicked butt -- the opposing commander fled and has a hard time even getting anyone to follow her after her cowardice -- but just lost their lord. They could have sat on the battlefield forever without anyone coming along to kill them there.
Gotta be an exception clause for that. More or less. Certainly less when someone has it in for him. Given his character, deserting his lord in the grip of dark magic would also have him thinking himself on the less side. After all, failing his lord twice in less than a month would be a real possibility if he ran off and never managed to find him again. Even if staying would be a guarantee of failure.
And then there's our heroine, who is not pledged to any lord. But as soon as I started to think of her contrasting with the hero, she primly told one of the other characters -- I think the lord -- that her father had forbidden her. Is he really expecting her to disobey her father?