Sorry, it is designed this way.
Please understand that each sub-user can have his own private storage, which is not viewable by regular users. Each sub-user has his(her) own DriveHQ logon username and password, so in a way, he is like an independent user.
As a group owner / admin user, you can edit the sub-user info, allocate storage and download bytes, share/un-share files to him, or delete/disable his account, change his password, or logon as his account. But you don't get to see all of his folders unless he shares them to you. If you don't want him to have his own folders/files, you might want to allocate 0 bytes of storage space to him. So he cannot upload files to his own storage, but must upload to the folder you share to him. As the admin user also can reset sub-user's password, you can gain access to all of his files.