The difference though is that Germany committing additional ground units to CAU means those units die R2. Japan committing additional ground units to secure SFE does nothing for Russia other than pull them off China - Russia can’t really counterattack them because SFE is a Japan deadzone with their fighters, transports, and BBs.
It is somewhat micromanagement, we’re only talking about 2 IPCs and 1 inf, but I still think you’re better off just giving Jap SFE.