Bhai sahab, kaisi baatain kartay hain ap, how can CNG installation be a different thing? You are playing with the engine and car's life. Do you see the OEM car accessories at the dealership? Yes. So, do you think that the dealership sends the vehicle back to the factory in order to get the installed?
As for as honda civic or city is concerned, they are offering factory fitted navigations and leather seating as an option, you can see that on their website. I myself got a 9th gen civic this month with ff navigation. Do you see any such thing offered by IMC anywhere?
When the ecomatic or whatever it was named version was offered by indus, it was marketed as FF installation that came directly from the factory. Hope you understand.