But where is this train going to ALD ?
This PF availibility issue is only at ALD and CNB of NCR, not anywhere else. This train is going via COI , thus hardly "PF Congestion issue" arises.
And regarding The slack between STA-COI , this is provided for every train which goes via this route. More than 3hrs (some even take 4hrs) is provided for every train to cover 170 km of STA to COI journey. Its so that they cover up their existing delays caused due to aggressive run in WCR region...
more... between ET-JBP-STA. By this train could cover up its delays and enters the Grand chord "On Time".
If slack is not given , then train would get delay arrival into NCR and Grand chord , and then every body knows how much traffic is there. Once you are out of your schedule , then you will never able to get priority.
This same thing is done all around india. For eg , just see how much slack is provided for majority of trains arriving BPQ , KIR , BJU , LKO/LJN kind of Junctions.