There is potentially 2 orientations in the exif for an image. One is for the image itself, and the other is for the embedded thumbnail of the image. If one uses imagemagick with the command "magick identify -verbose image.jpg" then you can sometimes see that there is something like this in the output: "exif:thumbnail:Orientation: 6"

The exif-parser will read out this value and return it when you ask for orientation. However, it might not be the orientation of the image, only the thumbnail. I've seen cases where the main image does not have orientation, but the thumbnail has. Some exif libraries will give you no value in this case, and some vil give the value of the thumbnail. I belive the best would be to seperate them, with different tag names, like imagemagick does.