Admin external storage is not user specific

Have I misunderstood something. When external storage is added by the Admin, it should be user specific, right?

User "A" should not be able to see the files uploaded to the external storage by user "B", right?

Steps to reproduce
1. In Admin add external storage
2. with test_user_1 add a file to the external storage
3. create test_user_2
4. file from test_user_1 is visible in the external storage to test_user_2

Expected behaviour
User "A" cannot see the files uploaded to the external storage by user "B"

Actual behaviour
User "A" can see the files uploaded to the external storage by user "B"

Server configuration
Operating system: ubuntu0.16.04.3
Web server: Apache/2.4.18 (Ubuntu)
Database: mysql Ver 14.14 Distrib 5.7.16, for Linux (x86_64) using EditLine wrapper
PHP version: PHP 7.0.8-0ubuntu0.16.04.3 (cli) ( NTS )
ownCloud version (see ownCloud admin page): ownCloud 9.1.3
Updated from an older ownCloud or fresh install: fresh install
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):
Connected an Amazon S3 Bucket

ownCloud log (data/owncloud.log)

Please paste possible errors in the following code block, see https://central.owncloud.org/t/how-to-find-webserver-or-oc-logfile-enable-php-logfile/808 for more info

Integrity status for oC9+
Stable

Login as admin user into your ownCloud and access
http://example.com/index.php/settings/integrity/failed
paste the results here.
No errors have been found.

This depends completely how you have added / configured this external storage:

A storage configured in the Admin settings is available to all users by default, and it can be restricted to specific users and groups in the Available for field.

-> https://doc.owncloud.org/server/latest/admin_manual/configuration_files/external_storage_configuration_gui.html#user-and-group-permissions