The Dimensions section says "Nether_true=true" for Nether Quartz mixed veins, as does the mix {} section.
The way variables get declared in the config is weird. Why would you include the value of a variable in the name? The Nether Mix section declares "OrePrimaryLayer_522" to be 522, rather than what I'd expect, which would be declaring "OrePrimaryLayer" and the value is the ore ID. I get the impression the code is only looking for the presences of certain variables and the value is immaterial. But then, I've never done any Minecraft mod coding - my experience is all with C++ and similar languages.