It was for the neuro-psychiatric epidemiology specialization. And yes, I spoke with Deborah Blacker who is/was the head of this specialization and she said the same thing about each having a bit of its own governance. I'm not too sure about how they are coordinating all the invitations, but it seems a little haphazard. Good luck!!
It does seem that way, based on thegradcafe search results for Harvard/PHS - it's all epi so far. I got some sort of email template from Ellen Furxhi, the epi department admin. It was very short and included a set of times when the potential advisor would be able to meet.
I got a Skype interview invite yesterday for the epidemiology track/subfield. But I don't know about others. Does anyone know if PHS does any in-person interviews? Or are final decisions based on the Skype ones?