The immorality of Facebook has no limits. Censorship? Check. Espionage? Check. Profiling? Check. Propaganda? Double check. Dictators of the world are envy of Mark ;)
And, why not? macOS is Apple’s IP and they have all rights to do with it as they want. Buy the way, Chrome/Node.js JavaScript engine uses JIT compilation too. Are they affected?
Well, that’s why Apple forbids use of private APIs in the App Store apps. If you built all your tech stack on the foundation of some peculiar nondocumented platform’s behavior, don’t be surprised when this stack breaks.