Daylight is unpolarized. Daylight can be horizontally polarized by reflection from horizontal surfaces, so the resulting glare is primarily horizontally polarized. Polarized sunglasses removes glare by absorbing the incoming horizontally polarized light, while allowing other orientations to pass.
LCD and TFT displays incorporate polarizing filters to control the display output, so the resulting images are polarized in a direction defined by their construction. The angle of polarization can be checked by viewing the display through a polarizing lens and by rotating the lens until the displayed image darkens or disappears. I have checked the centre console, nav and HVAC displays on an ’08 BMW 135i and an ’11 BMW 328i and found that the displays are polarized at 45° so they are visible through polarized sunglasses worn normally. Same for an ’08 Porsche Cayman console, HVAC and radio and the LCD displays on my desktop. The radio display on the BMW 135i is horizontally polarized so is not visible through polarized sunglasses worn normally.
I have a couple of portable Garmin GPS nav units. Their displays do not appear to be polarized as they are visible through polarized sunglasses at all orientations. Same for my iPhone.
The front facing display on my AiM SmartyCam HD rev 2.1 is polarized at 45° so is visible through polarized sunglasses worn normally.
The display on my AiM Solo DL is polarized vertically so is visible through polarized sunglasses worn normally.
The display on my AiM MXS 1.2 is polarized horizontally so is NOT visible through polarized sunglasses worn normally.
A secondary display that is not visible through polarized sunglasses is a minor annoyance. A dash logger that is not visible through polarized sunglasses seems like a serious design flaw, particularly when the manufacturer has implemented viable solutions in their related products.