Did you? Google FB etc. are hiring MIT, Stanford etc. graduates what a surpise :) they are hiring people who started coding when they were kids as opposed to people who picked up SE in college no way!
Good companies generally hire off of provable skills not "how early" you started learning.
1) Majority of employees at Google FB etc are graduates of top tech schools.
2) Majority of employees started coding and had interest in CS before college.
How likely you are to be good at CS if you never had an interest in CS before college :)? I have a lot of friends from Easternn Europe now working at Google, Apple, FB, but this anecdotal evidence does not change the fact that majority of SEs there are graduates of top tech schools.
On the second point, I think interest prior to University is certainly helpful but saying it's a majority is just an anecdotal conjecture itself.