It might not be 10x or 20x --which is hard to measure anyway--, but we've all seen programmers that are far far better than others.
What's crazy to me is why would anyone try to argue otherwise. Isn't the same true for EVERY other field of activity?
There are painters (e.g Picasso) that are crazily more prolific than other painters. There are inventors that are crazily more prolific than other inventors (cough Tesla cough). There are athletes that are crazily better than other athletes. Writers. Composers. And so on. On some of those fields (like sports) we even have objective ways to measure how better they are. But in all fields, we know there are geniuses, crazy good guys and average ho-hum dabblers.
So, why exactly, would it be any different in programming?