However, when I see, for example, cylinder heads being flattened on their faces, the tool approaches the cylinder head from the side on each rotation and doesn't instantly shatter, scattering lethal shards everywhere. Every time the bit passes over a combustion chamber or bolt or water or oil hole, it is yet another interrupted cut. No cloud of razor-sharp, sonic-speed tool bit fragments.
The same thing with cylinder blocks being decked. Somehow, no deaths or tool shattering.
What is odd is that "interrupted cuts" have been done for decades, if not centuries, and yet they only seem to be an issue when the opportunity to sell someone new rotors instead of having to spend the time to resurface the old ones arises.
Here is a video demonstrating someone resurfacing a brake rotor without everything everywhere shattering into pieces. Take careful note of the myriad of holes in the surface of the brake rotor.
Here's another one by Powerstop:
And a drilled rotor from a race car:
As you can see, if someone says the slotted or drilled rotors can't be resurfaced, they are patently, obviously, completely, and obviously wrong.