External attached storage feature shares contents between users?

I added an external storage account authenticating via SFTP according to the instructions here. Everything went well and the new storage option became available for all users in a specific group.

However, I was dismayed to find that when a user copied files into drive, the contents became shared across all users within a given group. Is this normal behaviour? How can this be avoided?

Hi,

if you make an external storage available to a complete group every user of that group has full access to this external storage and all files placed on it.

If you don't want this behavior you need to use subdirs on the external storage and specify that subdirs on a per-user base.