Laptops have very poor cooling. I have a Clevo laptop with a great processor but it will sometimes throttle itself to cool down. Great for small bursts of activity such as compilation but I don't understand how they could market these laptops as gaming machines. Running ffmpeg stabilizes the temperature at a healthy 96 degrees.
Modern powerful hardware has a hard time emulating a glass of water with good fidelity. Reproducing physical effects like ghosting is often harder than it looks.
There's a lot of different usages that may not heat the GPU as much. Also Windows might have better thermal management in the drivers.
CPU wise, Intel defines their TDP as the average heat dissipation, but the CPU can boost higher than this. But from what I understand they tell manufactures to design to the TDP.