You are right. As I have discussed on IRI before that the distance between Moradabad & Ambala Cantt is much shorter via Saharanpur-Jagadhri rather than via Sonipat-Panipat. So congestion in Delhi Area & this reason may be the factors which have forced IR to run most trains from Calcutta(KOAA/HWH/SDAH) towards ASR/JAT/NLDM via SRE. I think that Gurumukhi Exp is doing fine as a SF Train and is receiving decent feedback from people :-)