If you dont feel happy about spinning then you should not be instructing.
On a number of occasions a student has had a good go at getting me into an unintentional spin , what are the chances of a recovery if you dont practice once in a wile ?.
The only valid reason that I can see for an instructior not to instruct spinning is if repeated spins make him/her ill and then they should practice once in a wile to stay current.