The point of the GP argument is that the lack of decent cross-platform GUI libraries is astounding to game programmers because games are much more difficult and

The point of the GP argument is that the lack of decent cross-platform GUI libraries is astounding to game programmers because games are much more difficult and involved than GUIs yet producing a game that runs on multiple platforms is mostly a solved problem. The point is not to say "Why don't you guys do GUIs like games where you recompute the whole thing every frame?". Even the people who talk about immediate mode GUI are talking about the API of defining the UI, not the implementation details. It's perfectly consistent to have a GUI library that exposes an immediate mode API but retains a lot of state between frames and only does repainting when necessary. Also I find this talk about battery life in general disingenious given that more and more tech companies are converging on implementing applications in Electron which drains battery life very quickly.