You don't need additional monitors to overload the GPU you can do that with compute code alone, no actual graphics needed much less outputting graphics.

Also it's not terribly hard to prioritise scheduling such that certain aspects of the system remain responsive no matter how high the load, do that until you kill the resource-hungry process for exceeding hard limits and then display a popup sending the user to the apple store to buy an even stronger machine that's even more overpriced. There, done. That still wouldn't be a Mac I'd buy, but it'd be an Apple I'd respect, none of this "things are better when they're worse" kind of gaslighting. That includes thinness of devices, btw, modern Apple laptops are severely crippled by their atrocious thermals, the beefiest CPU doesn't do you any good if you can't dissipate even half of the heat it produces, when you can run all cores at full tilt for a full half a second before it has to throttle to a crawl to not melt itself.

Sidenote: Can OSX maximise windows nowadays? Did they get around to implementing it?