External storage rights management

I’ve setup external storage (S3 and FTP). Both have the same problem. I don’t understand why I can’t manage rights to these folders, as with local folders.
I’d like to be able to create folders inside an external storage (S3) and ONLY share that folder with a group, not everything on the external storage.

Someone please explain if I’ve setup nextcloud wrong, or this is a limitation of Nextcloud. If it is, please share why this is.

Thank you.

Playing around, I think It’s a bug for sure.
If I add the storage with no group in the sharing option, and share a folder inside the storage with a user or group, then of course, every user sees the storage. But then, if I make the storage available ONLY to the admin group, The user I just shared the folder with can still see the folder.

It is a very strange behaviour.