I don't really buy this. If it were true, they'd have no reason not to open up more of their software. Why not take the Hack out of Hackintosh, distribute the OS freely and let anybody run it on whatever hardware they please? The answer is obvious: their software drives purchases of their hardware. People buy Apple hardware because they desire Apple software. You'll be hard pressed to find somebody who buys a macbook but then primarily runs Windows on it.
It's not a matter of Apple "hardware company" or a "software company" that's important here, in this context. It's Apple being a "hardware or software or both" company, while Google and Facebook are neither hardware nor software companies. They're advertising companies.