This is getting a bit off topic, but your claim is entirely false. I'll be addressing this in my next small changes list, assuming it isn't updated in 1.6, which hopefully it will be. I've been asking for the jaguar to get the desert tag since last August.
There is a limited number of jaguars present in the Southwester United States, concentrated mostly in Arizona, near the US-Mexico border. Furthermore, there is a breeding population of roughly 200 individuals in Sonora, Mexico. The Sierra Madre is able to be classified as a desert.
There are numerous rewilding conservation projects in both the US and Mexico to increase and stabilize populations of jaguars and ocelots in the two countries deserts.
There is plenty of current physical proof, plus overwhelming historical data, that prove jaguars can easily adapt, survive and thrive in desert ecosystems, which I believe justifies them getting the desert tag.