Ah, they are very unlikely to get the top 100, but very likely to get e.g. 100 of the top 200? Now I think I understand the trade off they are going for (e.g. Getting 100 of the top 200 is more efficient and they are "good enough")
Look at it this way. If you're a cream of the crop programmer and you're looking for a job, Google has the most drawn out and arduous hiring process. Even if you apply there and start the interview process it often takes a lot longer than the industry average to get to an offer. In the meantime a multitude of other companies have probably already determined that you are an excellent programmer and tried their best to snap you up.
Google seems to be happy with the tradeoff they're making but I'm pretty sure their process is not optimized for getting the best people in the field.