I disagree. Most people wouldn't flip the switch. And by most I mean 99.9% wouldn't even know what the option does.
I think the real answer is: adding such a switch would be very very hard UX-wise. Also imagine what would happen to users that flipped the switch and then never knew how to turn it back off, or whatever. You get the idea.
People in universities (both staff and students) are always left-leaning; the mindshare of Linux in universities has always been big everywhere, it's not really a Catalan thing. Because of that, I'm not surprised they are enthusiastic about the Catalan language either, but that's not the case anywhere else, where people usually run their software and enjoy their entertainment in Spanish without making a big deal about the language.
I also believe Windows 10 has a good Catalan translation although I have never used it.
So what will be the cost of deploying Linux, retraining on Linux, and then going back to Windows?
These people can afford to make stupid decisions because it's not their own money they are wasting.
The only reason this is happening is crony capitalism: they want to do a favour to the local open source businesses (there are a few of them) which are friendly to the local government. They will get lots of support contracts. It's blatant corruption.