Sorry, a little late with this response, but want to see if I'm in the same field.

What I noticed in this long thread is that wedickinson never said what he saw, much less why he waved the flag off. I was always taught that unless you see the originating contact, then you shouldn't be calling an "Illegal to the Back". When I first started officiating, I remember making this "rookie" mistake. And what I remember best is my WH came and asked me what did I have. When I told him "Clipping" (before rule change), he asked me where the originating contact was. It was then that I replied "uhhh, didn't see it." He then told me he was going to wave the flag off since 1. did not affect the play and 2. we don't know if we had a legal or illegal block. The point was that at least he told me why he waved the flag off and didn't do in a manner that "embarrased" me.

I am very grateful to work with a WH who doesn't let ego get in the way. I learn alot with him.