Being very brief on this one, as it’s probably just a code doesn’t match the graphics problem. Accidently clicked Singular Strike with only 3 in Woe, but it learned it. Afterwards I respec’d fully out of Woe, and could keep Singular Purpose. Played around a bit more with the tree and Void Aegis seems to have the same problem, not requiring Future Mind.
That’s intentional? Well, time to look through all my builds and see if I’ve been throwing extra points at stuff. Weird that it seemed obvious with skill passives that I only needed one path unlocked to continue, but didn’t click with class passives. Maybe just because it’s fairly rare on the passive trees.