I've always taken that distinction to be based on the rather straightforward proposition that it's one thing to say that someone's been shot, but it's not very meaningful unless you can say who did it. To say that there's been a breach of privilege may be of interest in passing, but unless you have someone identified, for the benefit of the Speaker, to address the point, it's hard to find a breach of privilege.
If I understood your question correctly, and I may not have done, you need to know who it is that the allegation of breach of privilege is made against so that the ruling, prima facie or by the committee, can address the conduct of that person and whether what the person did in fact constituted a breach of privilege.