That’s not really what he said – he was using Resolve’s colour correction features as an example of how a developer has thought about how to make a complicated professional tool work in the context of a tablet device with a touchscreen. Colour correction was chosen because it’s something a video production company with a heavily Mac-sceptic staff is considering using an iPad for. (LTT’s staff complained incessantly when they started using Mac Minis for ingesting footage to the point where Linus had to give in)
His actual point is that running macOS on an iPad immediately ends its primary use case. It will, from that point forward, be tied to a desk with a mouse and keyboard. Developers will stop trying to develop for it in the context of it being a tablet computer rather than a laptop.
The current discourse around iPadOS being more ‘computer like’, macOS gaining touchscreen support and running macOS on an iPad is being driven by people who don’t know a damned thing about human computer interaction.