It doesn't matter whether 10x programmers exist. Programming is not a sport and as such, competition will only lead to narrow thinking, useless optimization and hatred. What we should really strive for is making programming a more creative activity where people learn from and inspire each other, not a competition. Oh and also, "finding the 10x engineer" feels like a hotspot to inject hidden bias into recruiting.
True, but if you culled the bottom 30-50% of programmers, how much productivity have you lost?
Aside from that, if all of programming is competitive it will keep a lot potentially very capable people from entering the field because not everyone (regardless of ability) is made for competition.