Actually this is NOTHING new. Only thing is that it is a Duranto ! Trains which are running before time are always stopped by train controllers, to allow other trains, which are trailing, to catch up and pass the train which has arrived early, so that the trailing train can make up its own time/adhere to its own timings, subject to overall restrictions on the route, such as speed restrictions, track layout restriction, neutral zone, track repair/overhaul, and so many others.
Who gave the idea that Duranto CANNOT BE overtaken? It can be... as long as it is before time. If it is late by some specific margins, it will get precedence then only. And that too, if in the opinion of...
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train controllers that it can make up, PROVIDED THAT other trains on the section are NOT unduly delayed because of the preference given to Duranto.
So it is NOT a big deal. If that were so, during the fog season, Rajdhanis should have got tremendous preference over other trains, including cancellations of other trains on the route so as to allow Rajdhani complete preference ! Correct? Good wishes.
PS: Incidentally Rajdhanis too get overtaken... look for that you will find it somewhere... and yes, it is true...