So, Mjolnir her/him/itself is -apparently- the God of Hammers. Unless something seriously important is revealed or changes as the story goes (and I don't think it will), this is a new level of stupidity imo.
Retcon after retcon after retcon after retcon ad nauseam for almost 20 years now. Pffff!
In Jason Aaron's Mighty Thor #11, Mjolnir manifests and speaks to Jane Foster. It says it took an enormous amount of power to speak to her like that, and it probably would take a century of rest before it could do so again. Mjolnir did it to protect her civilian identity.
I'm guessing Cates is building off this thread from Aaron.