It's a sad issue and I'm glad you brought it up. Many laptops will overheat and shutdown when tasked with 100% CPU and GPU loads.
I can't say this is a design flaw since you see this across many machines. For example if you were able to drive your car/motorcycle at 120MPH for extended periods it may shutdown or fail. Is that a design flaw or a limitation to the model?
The "gaming on a laptop" is something of a well worn issue with folk bursting into flames over the subject.