contact list : how to hide the names of other users in the "assigned to" field ?

Hello,

I have users belonging to a group only able to view/edit/list contacts they own , but when they are on the contact list screen (/index.php?module=Contacts&action=index&return_module=Contacts&return_action=DetailView) the name of all users appear in the “assigned to” list, even admin users.

Is that normal ?
I was expecting that the field “assigned to” would only list the names based on the user’s role settings.
In the list they are not able to see each others contacts, that is OK, but why should they see the names of all the software users ?

I could simply remove this field via the “studio”, but then other users with higher privileges would not be able to filter contacts based on the “assigned to field”.

Am I missing a setting in the admin ? Could anyone give me an idea where to look, or how to achieve this ?

I am currently running SuiteCRM Version 7.6.3 , Sugar Version 6.5.23 (Build 1061)

Thank you,
Miroslav