I quoted the relevant portion of your comment. Guido knows his chosen set of tools and standard libraries like very few.

He certainly knows Python much better than everyone using Python who is currently on the leaderboard.

He wouldn't be on the leaderboard because "knowing your tools and standard libraries" is only a small component of what makes you good at competitive programming.

I don't think anyone in this thread was implying that language devs are usually good speed-programmers, the relationship was in the other direction.