No, its the general display regardless of app. When wearing polarized bifocal sunglass readers, all is normal in portrait mode, texts, images, etc, but rotating 90° to landscape, all goes very dark. Seems a polarization issue, try it with polarized sunglases. Defiitely not a display setting.
That would explain the issue. Is there any remedy or setting that would counter this? Otherwise landscape mode is "NOT AVAILABLE" when outdoors using polarized sunglasses, which also includes prescription sunglasses. Not a good selling point!