Why should it cause jealousy and confusion if it is used on a dedicated route and doesn't have frequent plane swaps - I can imagine how peeved J & PE pax would be if that happened and they had to go from their 77Ls to AI older 77Ws...
Airlines upgrade their fleet all the time and that fleet upgrade takes places in a phased manner. BOM - EWR pax should not be jealous and confused if for example - DEL - EWR pax get the newer planes.
I do agree this is more PR/marketing gone crazy. Announcing 5 ULH routes with 5 new planes!