I'm not sure. I was told that it has to do with the polarization inside the IPS display, so this tip may work the same for other devices with an IPS display. Supposedly, it's polarized in landscape orientation, but not landscape.
That said, I don't know if this explanation is factual as I don't understand modern display technologies to a deep level.
In my experience, the polarization angle varies a great deal. Some devices are polarized vertically, some horizontally, and some at about a 45-degree angle. So, there's no set angle that works for everything, but what will work for everything is rotating until you find the right spot.
At that point you may end up with your head at a weird angle and decide it's not worth the trouble, of course.
That said, I don't know if this explanation is factual as I don't understand modern display technologies to a deep level.