You have been given the wrong answer. If a user submits a post that cannot be accepted, then that post will be rejected. However, there is nothing stopping someone from resubmitting the same project again as a new post.
EDIT: I was thinking in the context of translations. Looks like we have a grey area.
That is not true @dutch, we do not allow the same contribution again. This is why the Never submitted before rule is in place. This would also defeat the purpose of this change.
Source: I'm an Utopian supervisor... And consulted this with other supervisors just right now to make sure.