Actually, it makes a lot of sense that it would be the Protoculture homeworld. Where wlse would the AFOS take Sara 7 Shin" We know that from Macross 7 & Zero, the Protoculture left contingencies in place depending on the direction of human evolution. In Zero we have the AFOS to whipe everyone out of existence should humans turn warlike, and in 7 we have the Lux ruins which only become active if a human/Zentradi hybrid enters (i.e. humans turn out to be peaceful, and succeed in doing what the PC couldn't, tame the Zentradi).
But if you mix Humans/Zentradi/Evil/Ginga Kujira, you'd get something an aweful lot like the Vajra. Perhaps they're the Protoculture's final solution for peaceful life in the universe. What better place to birth such life than the start of all life to begin with? That they only respond to emotions through song definately speaks volumes.