You do not know who is in those groups. Under Islamic law, a terror suspect can lie and “say” he or she is a Christian. What documents could they provide that they are? A baptismal record?
None of them can be properly vetted.
I do know who is in those groups, actually. I’ve been actively involved in helping Christian refugees for the last few years.
I know the names of a large number of these people. I have seen detailed dossiers on them. Not all of them, but quite a few.