I think the important thing to establish here is there's a significant difference between having you delegate it on the portal and having an importer registered.
As has been mentioned, an importer can be registered and not delegate a service provider, which means that service provider would not know whether they were registered or not. To presume that every person who has had one clearance with a courier is a small business is not realistic. There are many importers out there that utilize a courier only for small shipments, but not the others.
Personally, I have set up most likely close to 300 importers, and every single one of them will ask for delegation from the couriers. If they don't use them, we decline that registration.
It's not realistic to believe that if they aren't on the portal, they were delegated. They have that option. The portal belongs to an importer, and they have that right. It's not realistic.