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.
They mention the impact that windows has on the CPU in the video. Then they switch to a more powerful CPU and show the GPU and Memory Bandwidth is a problem.