I've flown this route with them many many times over the past few years and I can remember at least 4-5 occasions when they weren't able to load everybody's bags because they didn't get the length of runway they needed to take off with a heavy load. Sometimes it was runway work, sometimes rains, visibility etc. I can tell you from first hand experience they do have issues.
I suspect it's the amount of cargo they get from BOM + having to go around PAK - can't be 100% sure of this of course.
If they wanted to make money they would have charged the DEL-EWR route because UA has temporarily stopped flying that route so they're the only direct flight. Most airlines doing BOM-NYC (1 stops) allow 2x23 so all they would be doing with this move is losing marketshare. Then again this is AI...