In that long podcast interview I posted a few pages back, Hickman basically says he had to use her to set everything up and put her back in the toy box for now, as she'll be used in the long run.I re-read all of Hoxpox and I'm still even more puzzled that we haven't seen Moira at all since.
I guess it wouldn't hurt to see her every now and then, except if her absence itself is supposed to be meaningful.
My best guess would be that the fact she's a mutant and that everything hinges on her is a secret in-universe. Hell, now that I think about it, only Charles and Mags explicitly know about her. I assume the council should too, but I don't think that's ever been stated. This, in turn, adds more weight to the threat of Mystique knowing about her.