Some people are just smarter than others - much smarter. These engineers have their brains wired differently, helping them be more suited to programming/design work. If we accept the existence of 10x chess players (state champions) and 1000x chess players (grandmasters), why not 10x engineers?

I personally worked with (and managed) amazing engineers that are AT LEAST 10x more productive than the worst AND average engineers.

Assuming that they are toxic or hard to work with is something people say to feel "the same when all is taken into account". That's not the case, a lot of these great engineers are great people too making them objectively a lot better than the average engineer.