Dude,
If a certain ability is unique to a certain core only, it
is called One-Off ability....
Other than One-off ability, everything else is kind of achievable by other IS.
Therefore Pseudo-shift is not unique to Sliver Gospel (in your story), other IS cores can do it too but Sliver Gospel (in your story) is the only one that do it so far....
Edit
Side note: It has been mentioned that Barrier Void ability is not Unique... other advance users can do it too....