I may be reading this wrong, but I think this means that a shot glass is mathematically perfect.
But maybe the shape of tee-cups and coffee mugs is optimal, in its own way? I certainly appreciate that beverages that need quite high temperatures for brewing are cooled down quickly to a drinkable temperature.
Alternatively, complicate things by taking the width of the glass into account or model convection more realistically (a square meter of glass close to other glass of similar temperature will not lose much heat)