This is now LIVE!
If the selected photo has a description in the EXIF metadata, that description will be used as the photo caption.
@Dimitri Cassimatis, as suspected, 360 photos are more complex. We will basically have to create a new post type only for those.
Feel free to submit it as a separate feature request. We will only take action if a lot of people want that. From experience, not that many people use 360 photos.