Some articles mention that horizontal and vertical dpi of screen could be different and yet Screen.dpi is float variable instead of being Vector2. Why is this static variable not Vector2?
If you have devices where DPI is different, then please submit a bug report and provide details.
But, back to your question, what problem are you trying to solve?
I believe some old plasma TV sets don’t have the full horizontal resolution, so they have stretched pixels, but that is unlikely to be an issue with Unity.
Some OLED screens do not have a full set of sub pixels, instead they are shared with adjacent pixels, but I assume they report a pixel as 1, even thought it doesn’t comprise a red, a green, and a blue sub pixel.