The problem is, you don't get shit for infiltrating the Absolute. Do you subvert their members and turn them on your side? No, outside of Mintharra, and that one is mostly by accident. Do you gain unique knowledge of your condition, that you wouldn't otherwise? No, not really. Do you end up in a better position against the cult? No, and if you were dumb enough to side with the cult during your entrance to Shadowlands, you actually end up in the significantly worse position, because you have to fight a very strong drider later on. Do you gain access to some unique tadpole powers? No. Do you gain acceess to some powerful cultist weaponry? No, you actually gain far better access to it when you side AGAINST the cult, which is... Odd.
The idea of infiltrating the cult to achieve some goals is definitely an interesting one, you can do things with it, but the game doesn't do anything.