Of course, but if he said the words and at that time believed, why would he not believe he wasn’t saved? That is us taking God at His Word. That is faith.
We are commanded to repent and confess. It's a change of heart. We are new creatures in Christ, not just cleaned up old ones.
When we are saved we are crucified with Christ and made new creatures, the old has gone and the new has come. If the flesh has been crucified with Christ, how can one not be saved?