I think that if the the allies were allowed to just NCM in to take control of a fallen allied powers tt’s (collect the income) it would swing to much income to the allies and break the game. Plus if your getting paid for all those tt’s why would you Liberate your former allies capital (kinda like how Paris is now). It is better to leave things as they are and they only get paid if they liberate them from the enemy. That makes a pretty good cat & mouse game of how much tt the axis want to take vs how many of them they will be able to hold later on.
If that were the case, then I feel the Axis original TTs should be worth double to Axis powers only. Sort of like the Russian NO, but reversed. But yes, I concur with your analysis, in-so-much in regard to Dutch/Netherlands.
I always viewed that rule as a way to not automatically give the income to England but not deny it to Japan either. It really only plays in the Pacific campaign, as your only chance to get the income is to invest enough to push Japan out (otherwise, Japan will crush any resistance and take it.)