As commented elsewhere not all viewers respects the orientation flag, and only display the native image. This is a viewer bug, not a bug in the app generating the images.
Even big ones like WordPress messes up when they create thumbs, If android displays it correctly, the flag is set correctly.
We do NOT want the camera app to reprocess the image in the resulting direction, it takes time, and comes at a potential quality loss. That is the whole purpose of the EXIF flag telling how many times 90 degrees the image should be rotated for display.
Sure decades ago before this flag, we DID r