According to the article the lower caste makes up 25% of the population, so presumably, 75% are upper caste. It means someone upper caste is 3 times more likely to be a techie compared to lower caste.
By comparison, a man is 4 times more likely to be in tech than a woman, and asians in the US are 10 more times more likely to be in tech than whites and 30 times more likely than blacks!
So there is certainly a gap, but a surprisingly small one considering the difference in status and presumably wealth and education.
Of course, it doesn't excuse the caste system, and especially not the difference in treatment at the workplace.