Author doesn't establish this, just takes it as a given. I wonder what features terminal emulators/editor programs would lack that are afforded by GUIs? I consider the terminal text editing experience far more efficient
Depends how you define better. If you do something very often a steep learning curve with long term payoff can be the better UX seen as a whole.
I use almost only VSCode mind you, but I can see the argument here. I know a bit of vim and it is practical when configuring servers via PUTTY. For bigger projects I find it very lacking.