Higher resistance doesn't equal more harmonics. What's needed is good technique, and an amp that responds well to harmonic excitement. You should be able to get decent harmonics out of an acoustic... so it's even more about technique than about gear.
Zakk Wylde does well with his EMG actives... Billy Gibbons does well with... well, anything you put in his hands, but primarily PAF-level humbuckers. Van Halen did well with a PAF, too...
In any event, it's mainly technique. But the right pickups will help. However, the "right" pickups aren't always going to be higher resistance pickups... it just doesn't correlate that way. Higher output pickups will be more likely to excite your amp, and higher resistance pickups generally have more output. So, Metalgoth isn't totally out of left field or anything... indeed, the second part of his statement is just fine... it's just that he's attributing the harmonic generation to the DC resistance rather than the combination of 1. touch, 2. amp, 3. OUTPUT level of pickups, which in turn goes back to point 2.
It might seem like a niggling point, but there are pickup technologies with far less resistance (Lace, EMG) but equal or greater output. The DC resistance can get you in the ballpark for output in traditional passive copper-coiled pickups, though.