I think Stamp Paper are just a way to collect duty on some specific transaction. Here in the case of Export they have specifically mentioned that they required Bond Paper. In the earlier VAT system they specifically ask for the Gurantee at that point of time Stamp Papers were also required.
Now in the consent letter they haven't asked for any specific requirement and also granting the registrations, so on what GROUNDS we can say that they will reject.
Thanks & Regards,