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.

Some cameras do overheat from extended recording sessions, so depending on the model it's not entirely a joke.

It's a joke, but it's also the truth. Many cameras won't even get to 30 minutes before overheating.

Yeah I knew what you meant. I have one :)

IT's not a joke. When filming for more than 30 minutes the cameras at the time (10-15 years ago) would warm up and eventually shut off automatically to cool off.

FYI many modern cameras still do this.