When I was teaching some nonsense at Tennessee at Martin, a professor of Indian origin was in the botany (?) department was there. I met him a few times.
He had a joint appointment with Harvard. That was impressive. Harvard and UTM are poles apart.What was he doing in Tennessee?
A few years later when in Japan I saw a news that a Harvard professor was caught cheating manipulating his research results. I believe it was him.
At stat there is a way to find if someone is cheating. One can never be sure, but if there is 95% chance of that happening we can claim that some cheating is suspected.
If 50% of JEE top 100 are from Bombay, while only 1% of test takers are from Bombay, to me the case is clear. Unless they are of superior species some more test are to be be conducted. Ask them to take GRE, GMAT. ask their parents’ test scores, ask their children’s test scores (many years later), and so on.
This being India, the people who would be hired to catch fraud, they will take bribes, and produce falsified report. That’s a most likely scenario.
I feel widespread cheating in JEE might be common. I ask my classmates, some high achievers, to produce their GRE and GMAT scores, and have never succeeded.