Restoring CSM, CSD with SIS file from an external hard drive isn't working with Steam's Restore Game Backup feature

[Reborn]

Steps I have tried:
1. Open Steam
2. Click on the upper left corner
3. Click Restore Game Backup
4. Browse and select the directory of the folder containing the CSM, CSD, and SIS files
5. After selecting the directory, the Steam backup popup window doesn't change

What I have tried doing:
1. Restarting Steam
2. Restarting Windows

What I am currently trying to do: moving the backup files outside the hard drive in hopes that it would work.

For reference, these are the images of my directory and what I tried.
- Backup files: https://imgur.com/a/As1LcyR
- Steam popup window not changing: https://imgur.com/CR1V4GO, even after browsing the right directory in my hard drive, it does not change

[Elucidator]

Try reporting the bug on https://steamcommunity.com/groups/SteamClientBeta/discussions/
and contact steam support.
(make sure you tell them you did everything as instructed in the FAQ
https://help.steampowered.com/en/faqs/view/4593-5CB7-DC3C-64F0
otherwise they will just redirect you back to the FAQ.)
and make sure that you make it clear that this a clear bug.

Unfortunately Steam Game Backup Files are propietrary so, I have no clue how they can be converted back to game files without Steam itself.