This sounds like bs to me. There is a significant number of users with profile photos that don't contain a face and this is the first time I'm hearing this...
Those users probably have performed various other actions that reassured FB they had not signed up to spam (joining groups, adding many friends, etc.). It was the combination of being a new signup with an emptyish profile and having no clearly identifiable face that led to my account being blocked, with a message that specifically said I would not be able to regain access to my account until I uploaded a photo where my face was fully visible.
