Second-tier compared to the world's top universities; that is, Harvard, Stanford, Oxford and their ilk. I've seen posts on this website[0] how some big tech companies almost exclusively skim off the top.
The notion that FB/Amazon hire primarily from the top 5 universities is so totally unrelated to reality that I feel like I'm watching people discuss the consequences of the fact that the earth is flat.
Perhaps to some extent some are optimizing for social class (staying in the one they grew up in).
Big tech companies tend to have interesting work. Why would anybody jump through the hoops to go to a top university to get an ordinary coding job?