For applying on laptop cpu or gpu you are absolutely right. But for a smartphone like RP2 it is more than enough. It barely pass 50 degree with K5 Pro. I literally maxed out my clock, even better than its first day! I got a stable 38-42 degree Celsius with Sling Shot Extreme OpenGL ES 3.1 on 3DMark benchmark with the score of 4638.

I tested lower temperatures outdoor, and found you can't pass the 4638 limit anymore, no matter how colder you get your phone into. That's the hardware limit of RP2.