You could always distribute them evenly, but that's not what this guy was talking about. He was talking about intentionally stuffing
Am I the only one who didn't miss the obvious?
You can not "stuff" anyone, intentionally or otherwise. Unless they want to take the estate, it's not going to happen.
"Ah!", you're going to say next, "core regions will simply not be offering estates! Ha! Stuffed 'em!".
Not so fast. Core regions will suffer, if they don't have enough knights. So they will offer estates, until they are full. And as long as they do, the deals at the border better be good deals, or people will take the other ones.
I think one of the main problems people have in conceptualizing BattleMaster is that you approach it like your average computer strategy game, where one player is making all the decisions. But that's not how it works. And that means that other people in your realm think differently. Maybe
you wouldn't be offering 25% when you can get away with 20% - but they do. And that's why they get knights and you don't. Hypothetically speaking.
What I mean is that you can't approach the whole thing with a mini-max attitude, because doing so you make a fundamental erroneous assumption: That everyone always behaves rationally, and in the way you think a rational person would. Don't feel bad, it's the same mistake economic theorists make all the time, which is one of the reasons most 1st world economic politics are !@#$ed up, but that's a different topic.
There are many, many reasons why a lord would do something seemingly "sub-optimal". Maybe he doesn't want to be bothered with running an estate of his own? So he cuts large estates with a good tax rate, but a high lords share. Or he is aiming for political power within the realm and wants to attract as many knights as possible, so he makes better deals than strictly necessary. Or he wants to share the region income with his good friend, and thus cuts it in two 40% (max for his region) estates and leaves the rest as wild lands, even though that's wasteful.