It's mostly right. I had one of these temporarily wired so I could instantly A/B what he's talking about. In that pickup, only the top coil really senses the string & generates signal, since the magnet poles don't pass through the bottom coil and there's a metal shield between the halves. When you switch to only one coil, you get more output and a fuller sound because the pickup isn't loaded down by the extra coil (which adds resistance but no signal). Of course, you lose the humbucking effect, too.
If he meant that it was fuller than a stock STRAT pup, yeah, maybe. I'm pretty sure it uses 43AWG wire instead of the strat's 42, which will roll off some highs; it's also wound a bit hotter - around 8k compared to 6k for a typical strat.
As for reducing the noise when the bottom half is out of the circuit, I don't buy it. I couldn't A/B that aspect, because you have to physically remove the pickup to remove the bottom coil. Since I only use the middle pup in combinations, I permanently removed the bottom coil (when combined with other coils, you can still get a humbucking effect). I didn't notice any difference after doing this, but human auditory memory is short. But then, so is Eric Johnson's. I don't know of any magnetic theory that would suggest what he describes, but I'm no pro, either.
Incidentally, I like this pup a lot. Ibanez's C2 is the same thing, and you can often get them cheap on eBay...