Single dosing requires finer grind settings since less beans are going through the burrs at any one time and they are less likely to crush each other, i.e., the beans do less work, so the burrs need to do more. That part has no effect on grind quality.
The efficiency with which burrs suck in beans varies dramatically, both by the burr geometry and the coating on the burrs (Bunn Turkish and regular burrs are identical but for the coating, and the Turkish burrs suck in beans far better). There are some grinders that can grind down to Turkish fineness with a full hopper and can't even manage an ordinary espresso shot when single dosed, the excellent line of Eureka grinders, for instance. This obviously does affect the grind quality.
Conical burrs are always excellent for single dosing; flats can be tricky. I'm guessing when Denis is choosing burrs for his Monolith flats, he has to do a lot of testing to find those that work well.
Quite obviously, Scott Rao has absolutely zero experience with the Monoliths or any other purpose built single dosing grinder, otherwise he wouldn't be pontificating. This ignorance is par for the course when it comes to commercial espresso gurus talking about high level hobbyist practice. We listen to them, probably too much; while they have no clue about what we are doing, and how much better than them we are doing it.