Now, several members of this forum including Mor Ephrem have stated that the prevailing Western idea that the Indian Christians were Nestorian prior to the Portuguese invasion and the alignment of the Malankara Church with the Syriac Orthodox, is false, and instead have affirmed the historic existence of a genuine Orthodox faith on the subcontinent, contemporaneous with the Nestorian church which was forcibly converted to Rcism (the Syro Malabar Catholic Church).
My argument is not that there were simultaneously an Orthodox East Syriac Church in India and a "Nestorian" Church in India when the Portuguese arrived. There was only the former. An internal division within the Syro-Malabar community in the nineteenth century resulted in the creation of a "Nestorian" jurisdiction.
I am also curious as to whether the East Syriac liturgy used by the Nestorians was used by the Orthodox as well.
Every indication we have leans in this direction, but unfortunately most of the written record was burned by the Portuguese.
Your post raises two interesting possibilities: firstly, if we say the Indian church was entirely Orthodox, would it be not unreasonable to assume thst substantial portions of the East Syriac church destroyed by Timur the Lame, for example, in China, Tibet, Mongolia and Central Asia, were in fact Orthodox?
Secondly, does the possibility exist that portions of what is now the Assyrian Church of the East in Iraq and Iran were at one time under an Orthodox hierarchy, and perhaps came under control of the semi-Nestorian hierarchy (of Mar Balai and his successors) as a result of the confusion of events of various persecutions and the genocide of Timur?
Where what you say becomes really interesting is if we suppose a roughly coterminous Orthodox and Nestorian hierarchy in various East Syriac regions, and then add to the mix the interesting dimension of Assyrian tribal politics, which would later result in, for example, the Chaldean schism. Fr. Ephraim of the Assyrian church (who went to SVS, and for a time was a priest in the Antiochian jurisdiction) told me once that he considered the recent schism beteeen the Assyrian and Ancient Church of the East to have been perpetuated, if not initiated by, tribal political factors.