With the points you have presented I think we can narrow it down to two possibilities. One, the Hive gods Ahamkara are special Ahamkara that have the ability to commune with the darkness, while other lesser Ahamkara were hunted down by Guardians, or two, that some sort of Darkness-infused parasite infected some Ahamkara and made them able to commune with the Darkness and able to do things normal Ahamkara wouldn't. I think the second one is a tad more contrived, but you never know. We really need to learn more about the Ahamkara to better understand their abilities and purposes, here's to hoping they get brought up sooner rather than to more likely later.