I recently made a thread documenting a lot of weirdness, and it can be pretty game breaking for smaller nations. The rules for who gets the province immediately upon occupation do not appear to be consistent, and often a faction leader will refuse to give you land.
In extreme cases, I declared on a nation, took it while entering only from my own territory, and the faction leader was credited with the WC to make them a puppet before I got a turn:
Elsewhere, I capitulated Turkey and Italy got all the land (unlike Germany Italy would give me stuff I wanted), but then we get this weirdness:
So sometimes we keep the land after all. This is an example of the game's automatic occupation "logic" in play:
I declared all wars in SA. It nearly every case, it was either exclusively me or me + minimal help from other fascist nations there to capitulate the targets. Germany gets control because reasons. Sometimes, the factories/resources from land during a war really matters and occupied land is a substantial proportion of industry on average across a game, so this really needs to work better.