OK, after looking at the description for lightningrod, I know what has happened here. In gen 5, the description for lightningrod is this: "Draws in all Electric-type moves to up Sp. Attack." but the description for lightningrod in gen 4 says this: "The pokemon draws in all electric type moves." and the gen 3 description states that lightningrod: "Draws in electrical moves". What has happened is that the effects of the ability have changed over generations, so in gen 3 it just pulled electric type moves in, instead of absorbing them/turning them into spatk.