the connecting factor is true. But KCVL-SBC has PM at KCVL, Ananthapuri has PFTR in TVC. Obviously KCVL-SBC wont have day time PM slot available at TVC.
Parasu had PM at MAQ, but a Over night stabling line was available at TVC for Parasu. So 12678 can easily be extended to TVC. 12678 is a lean performer in case of reserved seats, I agree for obv reasons that patronage for ICE wont reflect in reservation statistics, but it can cater as a load reliever for JS,Ernad, Parasu, Venad and also UR travellers of Rapthi group, Netra, Sabari etc.