I have never heard of AEF formation flights either, and it is my firm belief that this would never be attempted on an AEF. I believe the accident theory behind the "formation flight" is being perpatrated by certain poor-quality newspapers whose only good use is for wrapping chips in.
I cannot recall there being an AEF accident until now, and the Tutor itself has an excellent safety record. I will thus refrain from theorising as to causes until the AAIB has done its job and a report is published; as the saying goes, "It will all come out in the wash".
I suggest, out of respect for the victims, that perhaps others also do the same.
Smithy