If employees are on the Time Entries screen and have filtered the screen to show by Project, CORE shows every project, regardless of whether they are assigned or not to them. This is by design.
In another case, if a project is left unassigned, it becomes visible to everyone. It is grayed out because it remains unavailable. To fix this, you can assign yourself to the project. As long as there is at least one person assigned to the project, the project will not be visible to everyone.