My guess would be illustrating what it would look like if IndiGo had a freight service. Still not a good explanation for the winglet job though. Perhaps the art

My guess would be illustrating what it would look like if IndiGo had a freight service. Still not a good explanation for the winglet job though. Perhaps the artist felt the Boeing ones look more modern? Or "if we had a freight service, it would be on Boeings"?