Same problem as ~4 years ago when people first saw the iPad: "What exactly is it?" "It's iPad." "How do I quantify it in my paradigm of notebook computers?" "You don't."
You're trying to quantify it as a smartphone. Facebook is positioning it as...well...a Facebook.
Frankly
They aren't trying to communicate anything other than attractive people. The target market doesn't know or care what "htc" or "android" or "lock screen" etc are. The target market spends money to be attractive people.
I wasn't drawn in enough to read all of the text, but I did take in the headlines and subheadings. And form all of that I left with the impression that it was either:
a. some sort of app for Android (standalne) b. an OS (some kind of lite version of Android with just Facebook social features) and/or; c. a phone that Facebook were making with HTC;
... or some combination thereof.
I understand now that it's a homescreen replacement. But that certainly wasn't the impression I left with.