We are not Apple, we are just users like you. So we can't fix bugs.
Honestly, I don't see this as a bug. To me, it seems unreasonable to transfer things that are invisible-- after a transfer, I need to look to see if everything came out alright.
The "Hidden" attribute for a picture is just a check in a database-- it's not a property of the picture. A picture will appear hidden in Photos, because Photos sees the check and doesn't display the image.
Once a file is transferred , it's just a file, a packet of 1s and 0s. You have to use some app in order to see it as a picture. To appear invisible (oxymoron?) you'd have to be using a program that reads that check properly and applies it. The Hidden attribute is not a standard metadata field, so no program other than Photos would understand it.
If you would like to make suggestions to Apple, go here:
Feedback - Photos - Apple