Well. I guess this issue at some level explains why Professor Xavier has a long history of being a jerk.
There was a foreboding symmetry in this issue: Xavier being led by Sinister, and Jean being literally led on a leash by another Sinister.
With so much symmetry and rhyming, maybe Jean’s most recent death and now afterlife experience are another manipulation and attempt to corrupt the Phoenix. Her inner monologue toward the end seemed to be increasingly focused on Dark Phoenix moments.
If I had to hazard a guess: Mother Righteous is the Sinister that achieved Dominion. She knows Phoenix is most vulnerable when it (Jean) is respawning in WHR. So she is manipulating Jean / Phoenix to prevent it from resetting reality.