It's not a joke, older DSLR cameras would often overheat when recording continuously. My good old Canon 6D would overheat once in a while when used as a webcam with v4l2loopback.
Even as recently as the Canon R5 Mark I mirrorless camera (which you can still buy new), overheats within 15 minutes if you're recording 8K30 or 4K120.
