I'm not sure if the issue was that Orwell was unaware that the Empire's policies had exacerbated the famines (which seems mad now, but, again, there was sometimes this attitude that Bengal starving every few decades was some unavoidable natural thing like an earthquake*) or just that he felt any change there would be outweighed by what he probably assumed would be an overnight catastrophic loss of central government authority.Not exporting a quarter of its rice to England would probably have helped even without the green revolution.
Like the main problem with arguing that the British Empire was a guard against famines is the history of British rule in India was one wherein a policy of discouraging food stores and the encouragement of cash crops led to a decrease in food security.
Just reversing a lot of british policies would have done the job.
* Maybe the attitudes of some people in the US towards mass shootings could be a crude analogy here.