No, facebook doesn't. The good programmers facebook hires don't work on the legacy PHP code. They do stuff like sigma. Also, I am not describing a problem, I am pointing out that their perceived problem doesn't exist. If I can hire a good programmer and make them write PHP, I could also hire the good programmer and let them write in a tolerable language, so the mythical "its easy to find PHP devs and impossible to find anything else devs" claim is out the window.