The route between sewagram and Nagpur is too congested, frieghts every 10 minutes, and ajni pf is on mainline so instead it is made to arrive early at Nagpur jn for smooth passage of frieghts and pf availability is not much of an issue because it is made to arrive on PF3/4 which doesn't block mainline so other trains can pass easily, regarding TT it can be speeded up but it will lead to awkward arriving time at howrah.