Yes. I’ve known it to happen. I have never heard of the purpose of such call to decide between or among a number of applicants from that same high school, however.
Sometimes there are questions that can easily be answered by a GC that could make the difference between admittance or not.
At some schools, with some GCs, there are long standing relationships between the GCs and AOs. There could be more discussion about a student. The conversation can be initiated by the GC too
My one son’s GC did get several calls from AOs and it was surprising to me, as one of them was from a large OOS university where I would not have expected that kind of attention. His GC informed him of the calls.