While I can't speak for bret's original intention, I believe he was trying point out that a true synthetic can't adhere to an oily surface without first having some type of "activation" phase enacted.
Activation can come in many forms - with Zaino, it's the ZFX catalyst. With Klasse SG, it's the AIO (which chemically cleans and abrades (albeit very fine) to promote adhesion), and with NXT, I have to believe the solvents and Kaolin (we'll argue about its purpose later) that help prep the surface for it to adhere properly.
Now, that said, layering becomes sort of a moot point when you introduce solvents and/or abrasives with each successive layer, right? I mean, SG and Zaino layer just fine, but they're also pretty finicky about the surface to which they're being applied. Got a little oil on the surface? That's fine, but durability might be affected accordingly.
NXT, on the otherhand, has demonstrated that it does have some cleaning ability (I posted pictures over at showcargarage), and others have confirmed its cleaning abilities. This would make me question how efficiently it can be layered, and it also helps me understand why NXT can be applied directly over something like SFP or #7 without any apparent issues.
I'm not saying this is a bad thing, but it definitely doesn't help put NXT in the same class as a Klasse SG or Zaino, neither of which appear to have any cleaning ability on their own.