Accurate depiction of tasks within a project

Sometimes in projects a task is no longer needed. However, you do need to complete those tasks in order for the project to automatically close. It would be nice if we did not have to complete them in order to close / complete a project. As this misrepresents a true depiction of what actually occurred with the project. Perhaps a recommendation could be a task status (no longer needed) or (decommissioned). The project should accurately depict whether or not a task has been completed, after a project has been closed. You should not have to complete them in order to close out a project