But wouldn’t Google prefer “stock Android”? Well, the ability to replace the home screen is a built-in, fully supported Android feature. Google intentionally implemented it. This feature is, in fact, part of “stock Android”.
Android’s home screen is largely irrelevant to how Google makes money with Android. Google cares very much if you ship an Android phone with a different default search provider, with a non-Google default browser, without Google Play, or without Google Now. But replacing the home screen? Probably not a big deal.
An interesting counterpoint to the “Google must hate Facebook Home” assumption, but I’m not convinced Google sees this as a net neutral or win — no matter how much (or how little) it directly hurts Google, it’s a potentially huge gain for their biggest competitor, and that’s never good. To add insult to injury, their biggest competitor built this potentially huge advantage on Google’s own platform.
It’d be one thing if Facebook somehow convinced Apple to build Home into iOS. But to take over as the social layer of Android — something Google has failed to do for its own struggling Google+ product, probably because of internal conflicts — is truly sticking it to Google, regardless of whether phones infected with Home will still use Google’s apps under all of those disembodied heads.