Honestly, if I understood the answer to that, I wouldn't have brought myself to this afterlife, to begin with.

[ She's treating him just as she did when they first met. You'd think that'd be favorable, but it's more unnerving than anything else. He's silent for a spell, but it's obvious he's deep in thought. He just knows it's going to be his job bringing Grell back up to speed with how this realm works. And apparently remind her of who she even is. ]

It is more of an accepted title versus a literal rank. We are in purgatory, sworn to do a job until we're considered forgiven.