A reseller has the ability to upload any devices through their reseller portal, however it is their obligation to ensure that the device identifiers (IMEI or serial) are correct and that the organisation in question owns the devices, not another organisation or an employee. If the organisation does own these devices, can prove this, and can supply accurate device identifiers, please discuss this with a preferred reseller for assistance. It is up to the reseller if they wish to upload devices already purchased since there are consequences for resellers who upload incorrect data to the zero-touch portal.
This will change in future.