Here goes my very raw analysis:
1. This MEMU will be running ahead and behind 58017/18 KGP-ASN-KGP PGR respectively. So chances of demand for additional halt is low.
2. A. In UP direction(68085), it is faster than Purushottam between KGP and PRR. If you miss Puru at Hijili, you can afford to reach KGP and travel till PRR to try your second luck. If Puru is late even by 5 mins, you will get it. MEMU's TT can be optimised to arrive PRR by 08:20 Hrs. Well, still if you miss you can...
more... return by catching CKP-GMO MEMU and changing at ADRA to GMO-KGP PGR.
B. In DN direction(68086), if you miss Purushottam at PRR, your luck to catch again at Hijili is less. Though you may try but remember if you fail, your only way to return will be HWH-CKP/BKSC PGR.
3. Runs behind ASN-RNC MEMU in UP direction. You may easily get seat from PRR as people will prefer the prior option.
Overall, I would call it a optimised move from SER. Well thought for both commuters and railways.