Then you are not really using anything heavy on the processor or have the default governor changed :). Take gamecube emulation or native game Nba 2k18… as soon as 30 or so seconds pass the cpu goes from 1500 mhz to 500-600… the game/emu goes from 25-30 fps to 10. You hit multitask and the the governor stops throttling and you quickly get back to the game and its near 30 fps again… again for a few seconds. Theres an cpu strees app that runs into the background that forces the cpu/gpu to stay at 100% but after like 10 minutes or so playing the phone digievolves into an oven :p
Some old snap Soc had severe thermal problems but they improved a lot. 820 and forward outperform the same level exynos/kirin by a lot in real using (maybe not in bemchmarks but…).