Seeing as how GEO enfeebles aren't susceptible to resists at all I'd assume that this new system is implemented to be able to put an enfeeble on doubly. My guess is they're keeping it this way for the moment to make sure that when GEO is released there's no way that RDM+GEO could cripple an HNM beyond belief.

It's easier to give a little here and there on the way than to give a lot now and take most of it back later.