I tried importing some A6400 RAWs into Photos on iOS. Then I went to RAW Power.
What I see is the megapixels reported as 24, but sometimes not all the metadata is appearing.
These (portrait) images loaded without any rotation issues, both outside of Edit and inside Edit.
Perhaps your images are set in a way that is causing the app to be confused.
Here are two links to files on PhotographyBlog:
https://img.photographyblog.com/reviews/sony_a6400/sample_images/sony_a6400_02.arw
https://img.photographyblog.com/reviews/sony_a6400/sample_images/sony_a6400_04.arw
If you download these, and import into your device, do you see the problem with rotation?
Thanks.
–Nik