...
Hide Time Tracking add-on checks project level permissions and, in most cases, is not aware of the single issue environment, i.e. permission depending on the Assignee or Group custom field.
Therefore it is not recommend to use issue level permissions because Hide Time Tracking add-on might not hide time tracking information correctly.
Issue level permissions are correctly recognised only on the a full page single Issue View page - it (it does not include include Agile boards Issue Details view or Issue Search (Issue Navigator)/Navigator).
In other places, Hide Time Tracking add-on does not have enough information so it must rely on a project level permissions.
There is an open request on our backlog to solve that problem but due to technical obstacles it is not possible to hide time tracking correctly if issue level permissions are used within project.
...