It has longer route and will act as two different trains 1st mfp-pnbe 2nd pnbe- Rnc
No one will prefer 2nd part due to (a) long route between pnbe-Rnc (b) Islampur-HTE prior to this with sorter route (c) late night for other stations after PNBE
Isse achha via Munger-JMP - KIUL- GAYA to ranchi would be better