I happen to know that even getting accepted for a BA at the IIT requires passing one of the hardest university entry exam on the planet.
Okay... based on my 30 seconds of research there are about 33k undergrads currently enrolled across all IIT schools. Assuming for the sake of absurdity they all graduated every year (when in fact, for a three year program less than 1/3 would reasonably graduate in a year), and every single one of them became an H1B worker in the US, that would still only account for half of the ~65k H1Bs issued annually. In reality they probably only make up a fraction of a percent (if any) of that workforce, as if they're that good they don't need to engage in indentured servitude. So the quality of IIT grads is not a particularly useful data point here.