It's suggesting that the forked Android OS/themed homescreen skin (depending on who you listen to) will be titled Facebook Home, thus explaining the wording of the invite.
9to5google's sources don't seem to have much else to add, but even on its own it's a not insignificant detail assuming it is proved to be the truth.
It doesn't really discount any of the other popular theories doing the rounds right now (assuming we all now accept that an actual Facebook Phone (capitals intended) emerging on Thursday is as unlikely as it ever was).
We could be looking at a Facebook “experience” for Android that will debut on HTC hardware before making its way to the wider Android ecosystem, or we could be looking at a more formalised forked Android OS that will be debut on an all-new HTC handset.
In essence that last point looks to be the primary point of contention, certainly as far as Thursday's launch event is concerned.
While enough rumours have been doing the rounds to suggest some kind of HTC hardware developed specifically to best show off Facebook's new software is indeed on the cards, would Facebook deliberately plan to share its moment in the limelight with a new piece of hardware?
It seems doubtful, but in this crazy ole world of ours, who can say?