Is there a license that basically says: MIT License unless you’re FANG? Is that what people mean when they say a code base is dual-license?
So if you wanted "MIT unless you're FANG, in which case you get an even more liberal license", you could do that with dual licensing. On the other hand if you want "MIT unless you're FANG, in which case all rights reserved" you're going to have to come up with some custom license.