Hi StealthYeti,
Just as a point of interest … the law tag indicates the percentage content based on weight not thickness so because the density of an elastomeric gel is higher than polyfoam … listed by layer thickness it would be a lower percentage of the mattress.
It’s also true that the pure gel formulations are more costly materials … even than latex.
The soft solid gels are very different from the gel infused foams (mostly memory foam) that are quite common (and much less costly). You can see some of the different types of gel materials in post #2 here and more details and links to more information about thermoplastic or elastomeric polyurethane gels (including some technical details) in post #4 here along with a few thoughts about the category itself in post #8 here.
Phoenix