IMO the Thunderbirds have always been designed to give the Indian buyers a Harley look at a RE price.
With Harley setting up shop in India it doesn't surprise me that Royal Enfield would make the 500cc engine available in place of the 350cc engine they have been putting into their Thunderbirds in the past.
Except for the new production front fork, the new headlight, fuel tank and the disk brake it looks to me like the bike is just using the same T'bird accessories the old one used.