Liberating Territories - Rule Check

So let’s assume Moscow is taken by Germany and there are some empty Russian (originally owned) territories, that are still under Russian “control”.
In this case the other allies can neither capture nor liberate those territories.

Russia does not get any income from those territories, until Moscow will be liberated.

@rulebook:

The original controller of the captured capital is still in the game but cannot collect income from any territories he or she still
controls and cannot buy new units. The player skips all but the Combat Move, Conduct Combat, and Noncombat Move phases
until the capital is liberated. If that power or one on its side liberates the capital, the original controller can once again collect
income from territories he or she controls, including territories reverting control to him or her.
…

I usually refer to this situation as the “Deep Endgame” the point when capitals start falling or being traded, when this curious situation develops where you can steal an Ally’s territory. Your reading is correct and this can be very important, usually for US/UK after Moscow falls, but it can conceivably happen with any nation that gets knocked out of play. Here it may sometimes be in the interest of one side Not to take certain territories still controlled by the vanquished player, for the purposes of denying this guy’s still living ally, the chance to steal this income or production. Similarly it can sometimes makes sense, not to liberate an Ally capital for the same reason, if the income/production you “stole” from them is substantial enough. Or especially if the liberated capital is likely to just be retaken by the enemy immediately (which is worse than not being liberated at all), since the enemy can then double dip, and steal your purse again before you even get to mobilize new units.

I don’t think any of that stuff would have been immediately apparent to me either, it’s just hard to parse the rulebook sometimes, and the official wording. In TripleA you get a clear visual, like the first time you see Karelia or Caucasus or Soviet Far East turn from Gray/Yellow to Green! and it opens up this whole other world of the endgame, post Moscow collapse. Or if you’ve ever played long enough post KGF to see Japan take control of Italy, or long enough in KJF to see Germany take Manchuria. Then it starts to make a lot of sense in the 2v2 match up, why sometimes it makes sense NOT to take certain territories from a vanquished enemy. Similarly if you still have Russian ground units alive, who could conceivably retake a place like Caucasus, but there’s just no point if the Germans already hold Moscow, better to leave it alone for UK or America to take, so they can collect the income for it :)

The stuff is kind of weird to be honest, and can definitely change the situation on the ground, once capitals start falling.