It's a small small issue but still
When you go to render out still or animation it should not matter if you are in performance mode or not. I should still render it in the settings you decided. If I want to render out in low quality I should be able to set that in the render output (a checkbox for performance mode rendering) or just manually set the render settings to low.
It can be a bit unintuitive when you work in performance mode to speed up/see animations better and then you press render and forgot the performance mode on, you select your high quality render settings and then it still looks bad because of performance mode is left on :)