And I've never liked that. For Germany as an example (no, I don't play GER that much, I prefer the allies), Barbarossa launched from Romania gives lots of territory to ROM, not GER. I've always hated that in all HOIs. Its like I have to screw over my ally and preform some cheese to make sure I get the territory, even though I am in fact doing all the work.
I think there is a way in mods to fix it however. I've been focusing on JAP a lot lately, and BICE was giving Jap conquered Chinese territory to Manchuko (heh, even though MAN forces never leave their border). I told Panzeroo, and the next release and all subsequents have given all that territory to JAP, and none to MAN. Maybe there is a way to do it if there is a puppet relationship which JAP-MAN is, and GER-ROM and USA-UK are not.
Now one area I dont mind it, or lets say it gives a bit of role play, is allies invading Italy. USA vs UK, Patton vs Monty, a big pissing contest to see who can get more territory quicker.