Correct. The 12 IPC (one way or the order) comes from “the bank”. No nation actually looses that 12IPC.
By “taking back” we mean overall income. Japan by attacking Russia, cause Russia (and allies to some extend) to receive an extra 12 IPC… but, since it Russia looses ground, so income, the effect or that extra 12 IPC is reduced by the losse of income (by loosing ground).
Furthermore, and it’s my point, Japan will make more income. So Russia loosing 1 IPC (for Amur for instance) and Japan gaining 1 IPC (for invadind Amur in my example), causes a difference of 2 between overall income of those nations.
So, that Extra 12 IPC received for the non-aggression pact broken would be nullify in 6 turns if Japan holds Amur all that time. But since Japand won’t stop at Amur and will take surrounding territorries as well, I say that 12 IPC bonus will be nullify in 2-3 turns… and all following turns, it will be at Axis advantage.