Surely it's an air/ground frequency, with Seething holding the licence, and not an air/air frequency?
I never heard of frequencies being classified this way, I learned frequencies are associated with services and services are associated with regions of airspace.
Back to the original question: my R/T syllabus mentions "interpilot" communications and outlines how to do them properly (though I must admit I couldn't rehearse it all right now), so I really can't see what the A/G operator was whining about. Just a bad moment, probably, that has happened to the best of us, hasn't it.