A lot of laptops have software-controlled cooling and power management, but also a hardware override. If you lose the software control the processor won't downclock when idle and will instead stay at full speed, causing it to heat up and the fans to also run faster. Given that a lot of laptops have barely adequate cooling in the first place, it's not surprising that it'll be stuck throttling at the maximum regulated temperature with the fans at full speed.

A few years (more like a decade now) ago, there were some laptops (not Apple) infamous for overheating to the point of shutting down if you left them in the BIOS setup for too long, or used Linux.