I would think so because there would be more sensitivity if the non-Javanese are not represented at the highest level. Expect also that to balance a Javanese Monarch that there would be a requirement, official or otherwise, that the PM would be non-Javanese.
Now the PKI, I'm trying to imagine what would happen to them. OTL, they became very close Soekarno in the final years leading to the G30S. But in this TL, assuming Hatta holds on the prime ministership into the 60s, there's a chance the PKI would be hostile to Soekarno because of Hatta's continued presence and Hatta's hostility towards the PKI. Expect the Army to be even closer to Soekarno than in OTL.
I think Guntur's disinterest in politics is more because he knows he can't do much in Soeharto's political system (
https://www.google.co.id/books/edit...tur+pni+election&pg=PA101&printsec=frontcover). Perhaps different circumstances would allow him to be more interested in state affairs?