That's bs. I work for a big tech company, and do interviews for them as well. Most people went either to a state school, a normal university in another country, or a small liberal arts college. Very few big tech employees have degrees from the "elite" class of universities. The same is true for interviews, the vast majority of interviews are not given to the so-called "elite" class, and the new grads I've interviewed from said class are no better or worse on average than people who attended less prestigious schools.
But that's because most people don't go to elite institutions. The only way to know this would be to build as data set of all the hires at FAANGs, for example, and then compare students from elite institutions to non elites. I would imagine these companies are not keen on sharing this data though.
