Chad, you're 100% correct, and they're not BSing. The air gap has a very similar effect to degaussing a magnet. One can even simulate this on pickups with a bit of insulation tape, 2 or 3 layers on one side of the magnet in a JB makes an AMAZING pickup.
I actually hinted at this a little earlier
MikeM wrote:ceramic magnets fit, and then steel poles are fitted against or near the magnet
But the gist of Gearhead and I were getting at is that there's double the amount of string pull in that guitar which WILL detract from sustain (I have noticed this even with an A5 in a neck position). I just carried on "informing" about magnet specifics.
I also like ceramic humbuckers actually, my go-to brutals guitar has the JP set in, a Crunch Lab and Liquifire. It is aimed at doing one thing really well (And it REALLY does that).