Again, I don't know the answer. I'm not even sure what carnauba sap is.
As for that 90 percent figure, let's go back a step. There is a percentage of carnauba out of the entire product, by volume; presumably, this is what Griot's is talking about. Zymol's "standard" (my term) waxes (Japon, Carbon, Creame) contain 33 to 37 percent carnauba. Their "estate glazes" (their term) contain more carnauba than that, up to 61 percent for their Vintage wax (I had thought it was lower, but I just looked it up). FWIW, none of the other estate glazes mention carnauba sap in their ingredients, so one could draw the conclusion that the carnauba sap, alone, does not explain the ability to exceed Griot's claims.
Let's be careful to distinguish the percentage of carnauba (all kinds) out of the entire wax, by volume (33-61 percent, as noted above) from the percentage of white carnauba (or yellow carnauba) out of all the carnauba in the wax. The 90 percent figure I quoted above was for their Concours estate glaze. It contains 47 percent carnauba by volume. 90 percent of the carnauba in Concours is white carnauba, and 10 percent of the carnauba is yellow carnauba. 100 percent of the carnauba in three other estate glazes (Vintage, Atlantique, and Destiny) is white carnauba; they contain no yellow carnauba. I don't know whether carnauba sap counts as white carnauba, or yellow carnauba, or something else, so I don't know how you would specify the corresponding percentages for NSX wax. (Although I have heard from very reliable sources that Zymol developed their NSX wax after extensive discussions with the folks who designed and engineered the NSX paint formulation applied at the factory in Tochigi.)