You are correct in that your temps were rising but you didn't know it. Had you had the page with the engine, trans and oil temps and oil psi on, you should've been able to watch the temps rise.
My trans temps run around 168-172 under all normal driving and towing conditions. Only when I get to a steeper grade and it's warm to hot out does the trans temp rise. If my trans temp hit 180+ and I was under normal conditions that would've been a sign that somethings not right.
Anyway nice to see your dealer is getting it fixed.