2-man three-point coverage

This past Friday I had a game where my partner (as the lead) would not signal for three-point attempts in his corner (opposite me at trail). Thus, I had no idea what kind of shots were being taken down there, and had no signal to mirror. During a break in play I asked my P to signal those shots as the Lead, but he said he didn't have to.

I sent him an email today (allowing for some cooling-down); basically outlining the rules I thought were pertinent. NFHS Officials Manual: 2.3.2.A.5 (Diagram 2-16), which cover PCA of the lead. 2.3.4.A.1, which reinforces coverage responsibility, and 2.3.4.B.3, 4, 5, and 6, all of which deal with responsibilities during a three-point try.

He said this: "I don't care what the book says. They will teach the lead to show but not signal. The lead is responsible for paint play and the baseline. The show is for help for the trail. The table will/should always look to the trail for a 3 point make. In 2-man the only reason the lead is involved whatsoever is to relay it was indeed a legal 3 point make."

Maybe he does not understand the situation I mean (three-point try in the corner opposite the Trail)?

Am I understanding the rules correctly?

He used college mechanics most of the night, is this a NCAA thing? I know NCAA does not list 2-man mechanics, but I'm trying to figure out the disconnect here.