Now let's explain this:
Let's say your NVIDIA GPU is a writer, the greatest ever, but he doesn't write directly in a PC or a typewriter, she uses a secretary (your Intel iGPU) to type out the book for him, but not only the secretary writes the book, she also translates it from english to spanish, makes all the drawings, and all of this is done at the same time and in real time, the writer keeps talking and talking and the poor secretary does all the work.
Issue is, that doing all that, as you can imagine, is REALLY hard, the poor secretary can't keep up!, she has amazing skills, but can only do so much at once without telling the writer "man, shut up for a moment please, I'm in chapter 1 and you are already talking about chapter 4!", the poor writer has to slow down (a big hit in performance), the secretary cannot possibly keep up with such a fast speaking writer, so the book (frames) gets written slower than if you just gave the writer a direct access to the computer, no need for translation, no need for drawings, just type and type and type, so the writer (remember, your NVIDIA GPU) can go and write the book as faaaaast as he cans.
Unfortunately, your writer kiiiinda hates the publisher (gamescope) and while he speaks perfect spanish, something they require, he doesn't want to work for them, so unless they get in better terms (driver updates and fixes), you'll have to wait for his secretary to write the book... problem is, that your secretary lied in her resumé/curriculum, she speaks spanish... just enough to know how to ask where the bathroom is, so you are basically boned.