So here is the video proof which shows that Lords are cheated right in with full troop size after being defeated. It's rare to observe it directly but Taleworlds can't hide it from us. They do it with Looters and bandits as well, that's why you can never clean up your lands and take some breath. Villages are in constant pressure which increases the starvation problem. They come again as soon as you turn your back. That's not "game depth", that's just broken.
Just for the protocol: He had 63 soldiers when I attacked him. 40+ got killed (not knocked out). He spawns with 63 again. So there is something like a standard troop size which Lords get for free. With them they are able to raid villages or crush weak caravans immediately after you defeated them. You can't even take them into prison to reduce this effect because lords have magic keys to escape very, very fast.