I would change the error message in Carbide Motion from “unsupported command” (vague: unsupported by whom? why? especially confusing for users who are sure G10, G55 etc. are supported by GRBL) to something like “command not supported by Carbide Motion: interferes with zeroing interface”, or “WCS commands not permitted (see ‘WCS support’ in online help)”. That would eliminate some confusion.