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Most polarized sunglasses are oriented to try to block the glare of light coming off of flat surfaces with the light source and bounce ahead of you...the more to the side the light source is or the less horizontal the surface is, the less effective the polarization is. The easiest way to check the orientation is to look at a surface that has glare on it then while holding the lens away from you, rotate it. You should see the glare increase at some point, and be minimal at 90 degrees rotated from that point. If you have a camera polarizing lens, it's a bit easier to see the effect.
Few sunglasses have the orientation perfectly vertical, which would block the light rays bouncing off of flat surfaces ahead of you, which includes the HUD light projection, but slightly angled to account for the fact those surfaces may not be perfectly flat nor is the light source reflecting at the same angles. The angle of the light source affects what angle works best in polarized glasses (Brewster's angle), so vertical may not be best, and it would be different at the equator versus the poles, as the angles would be different and is why some polarized sunglasses will have better or worse view of the HUD.
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