You're forgetting they all read all the way through cracking the code interview, the most difficult math book in history.

Even with a top-tier company, recruiting top-tier employees, doesn't implie top-tier-interesting-work. I do think many of the top-tier companies do have good people, because they can pay for them, but it almost seems like it's a defensive move to keep talent away from other companies, rather than utilizing that talent to the utmost.

>Top-tier company != top-tier employees.

True, but it typically means top-tier interviewer...which would make it more difficult to discover areas where they are lacking.