Which parts are not true:
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.