Agreed. I once worked with a programmer that took 3 months to figure out how to send a socket message... She had "30 years" of programming experience and refused to let me help her.
However, assuming some minimum baseline of having a clue, the multiplier is more likely to be due to environment.
Banks hire some very smart people, yet are historically aweful at delivering software. Startups, especially outside SV often have to survive by hiring "scraps" for peanuts, yet run rings around big corps.
If a company forces people to work with their hands tied behind their backs, they shouldn't be surprised results are lacking.
I've had small coding issues where one dev takes a path that costs them an hour or so, and another is able to deliver the same functionality in minutes.
I've seen projects where some developers simply say " I've no idea on even how to start such a project ", and other developers sit and think, read, and end up delivering. That's far more than 10x.
Environment may be huge, but it's blatantly false to say there is not a massive, order of magnitude difference between individuals. Unless you define developer as meaning within a certain competency bracket. At which point it's only true on definition.
What does having a clue mean though? Being able to code a loop? Fizzbuzz? SQL? Google for stuff? Architect a small program, a medium program, or a large program? There's a huge variation in cluefulness -- which is entirely the point.
I don't think this is true. It's quite common to have a huge productivity variance between people on the same team.