This is standard from what I understand. As it has been explained to me in the past, what happens is once the domain has passed expiration it is actually renewed automatically at the registry level,until or unless the registrar issues a command to delete it. Within 30 - 45 days from the expiry date the registrar will keep the domain in a 'grace period' where you can still renew it with them. If you do not renew during the registrar's specified grace period they will then issue a command to delete it from the registry and it will go into the next phase of the drop cycle, I myself have only ever noticed this happen on .org and .mobi domains, but I've been told it can also happen with .com and .net