His reasoning is pretty flawed, just like it was for DOOM. The OS takes up resources, Windows using A LOT more than the Switch OS, the performance of his build to how Switch will handle it is not 1:1, and some of these ports devs have reduced geometry and lighting to improve performance. That doesn't mean a port is possible. It just means that DF's reasoning on why it isn't is pretty off-base.
Still Doom was able to run in 60 FPS on PS4 (best refference, since the PS4 OS is also pretty light). So they could make the Switch 30FPS. Which is a big thing since the power required for 60FPS is pretty big. The PS4 can barely run the Witcher 3 in 30FPS. So expect the visual difference between the Witcher 3 version of Switch and PS4 to be much lager than those of Doom,which where already pretty big. Doesn't mean that it is impossible of course just a huge amount of work.
Please excuse my (probally) poor grammar