My understanding is it's mostly just the advantage of not having windows running hogging resources, so it should be a bigger gain for CPU bound games.
**Edit ** There can be performance gains from using vulkan over DirectX too, so there probably are GPU gains as well. It will depend on the game though
Yeah you're right, I had mostly been looking at the difference between the steam deck and legion Go S on that chart and barely even noticed the difference between windows on the legion Go S there.