Dear querist,
After thorough study of "Advance Authorisation" in Foreign Trade Policy and Procedure of refund claim in CGST Act read with IGST Act and CGST Rules and Customs Act, I am of the view that this issue is worth fighting. 'Advance Authorization' and Rule 96 (10) of CGST Rules are not an hindrance here.. IGST was paid which was not required to be paid. Hence such refund claim falls in the category of "excess payment of IGST by mistake". In other words, "Any Other Category"
This is altogether different refund claim wherein Rule 96(10) cannot create bottleneck. In order to get fair justice and relief, you require penetrative study of all the relevant notifications in this context. Too much hard work is required indeed.
It is worthwhile to mention that sometimes SCNs are issued to save one's skin.