2 years later this still isn’t especially clear to me. I’ve tried similar to what you’ve tried in the current version with no luck. I think the problem is that they already disable ShadowCRUD in the plugin:
and then they manually add resolvers for the mutations and the me OUTSIDE of ShadowCRUD:
The only thing I can see to do is to override the mutations with custom resolvers and throw an error. It doesn’t remove the mutations from the data schema, though, so it’s not really an answer to your original question.