Africa will provide about 3X the ipcs each turn that India will.
And don’t forget that the African Ipcs are most likely to be German rather than Japanese. It makes a big difference to have Germany at 30-33 as opposed to 39-42. 3ipcs(India) makes little to no difference to the Japanese in the grand scheme of things. I see big problems with a Japan first strategy primary among these are that Germany can get too big and walk through Ukr, Cauc and eventually take Karelia. If there are no masses of Allied troops preparing to take WEuro/FinNor then the Allies are in big trouble even if the push against Japan is succeeding.