Yes, you are correct, the SVM connection should be fine since SMBR only send something like a get-version zapi to the storage. If it gets back and answer it assume to be talking to a NetApp storage hence validate the license.
So, did you double check also that the SVM can talk back to the Server over HTTP? maybe checking it with whireshark can kelp.
Another option could be ot request a license file and upgrade to SMBR 8