That's simply sectional priority whch has plagued train run across Trunk Congested route!!
NER/ECR train via LKO/ALD on CNB-NDLS route always prefer high priority for clearance..even whn bot required as likes of REWA/Purushottam etc will nt distrurb thm..
Purushottam is even low in priority over Brahmputra Mail nwdays..