That is not how an RCD works. It doesn't even look at ground. An RCD will trip when the difference between the current going down the live and neutral conducto

That is not how an RCD works. It doesn't even look at ground. An RCD will trip when the difference between the current going down the live and neutral conductors exceeds a certain value -- in normal operation they are opposite and cancel each other out. If it operated how you describe, it could never detect someone touching a live conductor, because the current would not return through the ground prong.