Bad metaphor to use on me since I've ALWAYS supported that technique despite how often other people malign it. Never mind that Pikachu has kicked the shit out of plenty of other Ground types since as far back as the fifth episode, but maybe I'm just too logical for magic monster fighting: If the monster is covered with rock armor everywhere except for the big METAL CONDUCTIVE THING CONNECTED TO ITS BRAIN, then yeah, my rationale is to aim electrical attacks at that.
(Spoiler:) Thunder Armor on the other hand is bullshit that I'll never defend on no less than three separate grounds ranging from Pokemon physics to our own, before you start strawmanning with that.