Maybe we're thinking of different things, but isn't the backlog for Indian citizens caused by a fixed number of visas per year and per country caps? If you track the visa bulletin [0] they call out when a green card number is ready for your category, and India has its own set of dates because their country is so oversubscribed.

0 - https://travel.state.gov/content/travel/en/legal/visa-law0/v...