Well, as I said before, I believe the AA crews had trouble with azimuth calculations due to the desynchronization, which would lead one to believe that maybe it was a purposeful ploy. Certainly the single Heinkel and Dornier aircraft that I recall hearing at night had desynchronized engines. It was nothing to do with multiple aircraft in formation.
I understand RAF bomber crews did the same thing, but don't have a reference yet.
would be interesting to hear from an AA crew here.
Bob C