I suppose it can be thought of as a bug. "They" (almighty ca) have put into the patch a fix to make rebellions (and, by extention, reappearing factions) a bit more realistic. They will have a more normal mix of troops.

------------------
"You there, knight!" "Yes, sir?" "We just lost that battle. Why did you order your men to charge that unit of enemy sergeants?" "Uh, I was impetuous, sir" "'IMPETUOUS!? Impetuous!? Men! Kill him, I want his head!"