@hidden-account
Please see the response from the developers below:
Please note that if a tab or field is added, the user should be able to manage it. The “Who can view” option is designed to restrict content from other users, not from the current user. This means that if a field or tab is added, the user will be able to view/manage it.
If you want to restrict the content from being viewable or editable, there are currently no settings for that. However, we’ve added this to our to-do list and will implement it in one of the upcoming versions.