There is pretty tight continuity between the writers of WW Rebirth, for better or worse, so it's nice to see Wilson use Grail and paying attention to what Robinson did do an extent. I think that's the majority of the reason Grail is mentioned here, she was trapped with Ares in Robinson's run and addressing his freedom would naturally mean addressing where his cellmate went.
Black Hand is a Silver Age villain who wasn't being shoved down readers throats as the new badass arch nemesis, though. They came on strong with Grail, and she got a mostly lukewarm reception. Revamping some older WW villains or Wilson creating her own makes more sense than continuing to try with Grail at this point.