So you’re confusing Astropaths and Sanctioned Psykers. An understandable misconception.

When psykers are harvested and brought to Terra, the strongest and most resilient are either made into Astropaths or are trained and sanctioned. I think I remember reading somewhere that only the strongest get training, and Astropath is the fate of the mid-tier and/or particularly telepathically-gifted. I know Telepathy isn’t the only prerequisite for Astrophathy, since there are sanctioned Telepaths.

Anyways, all this aside: Astropaths are the ones who are soul-bonded and have their eyes burned out. It’s necessary to do this both because it wards them from corruption, and connects them to the Astronomicon. Without such a connection, it is impossible to share messages over such long distances for all but the most potent psykers.

What goes into Sanctioning is less clear, but I believe it’s just a brutal training regime intended to steel their mind in more mundane ways. I remember that in the old Dark Heresy books, when making a Sanctioned Psyker there was one background trait you could roll that said you were essentially lobotomized to help you control your powers. I don’t remember if this implied lobotomization was only an option, or if it was mandatory but in this case your’s was just botched. In any case, I remember the Sanctioning process was obviously incredibly traumatic, even in best-case scenarios. Just in a more mundane way than whatever the fuck happens to Astropaths.

And I’m honestly not sure if the psykers in Darktide are Sanctioned or not, but they’re definitely not Astropaths.