AFAIK Takeout + Photos returns the original image file exactly as it originally existed, EXIF intact. Any
additional metadata you have added manually is placed in a JSON file with the same name, adjacent to the image file.
It sounds like you want Photos to somehow merge that added metadata back into the image files, altering them. I'm quite confident that there would be an equal number of people complaining about changing their originals, if photos did that.