The letter was sent for RBL-AME doubling when it was single route!! Its no where written for third line but a track in RBL & AME Constituency!!
AME-RBL need third line...Hardly 17-18 one-way trains with Marginal Freight Load needs third line...Give everyone a break!!
With this logic, LKO-CNB & DDU-PNBE need Quadruple & SLN/FD-LKO need Triple track!!