In that period the Cold War was on. India was regarded as a defacto Soviet ally what with the Indo-Soviet Friendship Treaty etc. and there are certain references (have to search for them) in which it is clearly stated that India was a target for the West alongwith the USSR in the event of nuclear war between the US and the USSR.In late 70s there used to be a coffee table picture book form UK on total nuke war etc. It had a map of places which could get hit. I counted ~45 such places in India in those days itself that are in cross hairs even withtout any capablities.
But we are not living in the 1970s now.
IMO, the answer relating to the deliberate fog of confusion relating to TN lies in the JS-Talbott discussions immediately after POK-2. My theory is that there is an "understanding" entered into then which has also been honored by the current GOI. Hence the tightrope walk between on the one hand declaring deterrent abilities of "upto 200kt" to deter opponents in the region as the FT article states, and on the other hand"capability of making TN". I also believe that the Indo-US nuclear agreement is a by-product of that "understanding".
IMO maximilists within India do not want to be bound by such strictures and hence the current disputes.