I wouldn’t call this “IFR (VR)” graphic options. This applies to any flight conditions and non-VR gaming. Some people for example change render scale to 70% in 4k (non VR) to boost frames. Good luck reading for example the engine gauges on the G3000 without zooming in when doing that.
It’s just about having the render scale separate for the cockpit and the outside world. I’m OK with the world being a little bit blurry, but the cockpit should always be super sharp. I know both DCS and Aerofly FS2 do exactly that. The outside world might not look very nice there, but the cockpits are excellent. Especially in DCS.
I suggested that some time ago here: [Request] Seperate world and cockpit render scaling - Archives / Bugs & Issues - Microsoft Flight Simulator Forums but it didn’t gain much traction.