I don't think that there is necessarily a causal relationship between the salaries and the competence, but that line of thinking is common in those companies.
You're describing a good manager, who costs a lot of money, even more than a good SWE.
Maybe the high salary is to compensate for something else (poor work environment, boring job, etc) rather than attract very skilled people?
Look at CEO pay, most CEOs are clueless. They are way overpaid. Google is a perfect example, that business is a cash machine, it could be run by a ham sandwich, and they are paying people $100m+ to run it...lul. Jokes.
Btw, this also shouldn't matter. If your business relies on hiring these 1 in 1000, super-smart individuals (ignoring the fact that it is statistically impossible to actually do this if you are hiring thousands of programmers), you will fail. Every time. You get into a bidding war, and your budget depends on the intelligence of others to not overpay. If you can work out how to turn average employees into good ones, you will print money because no-one wants average employees...supply is infinite, you will never overpay (I know companies that have done this...they usually end up acquiring the companies that hire the "boffins" and fire everyone on day one).
In tech, the opportunities for this are basically limitless. It is pretty easy to teach someone how to code, the main challenge is really all the stuff you learn "on the job"...and guess what? You have a job to teach them. Why doesn't this happen? Try telling a coder he has to help a junior guy out one day a week and stop fucking about with Haskell/burning cash. Try telling HR that you want to hire unremarkable people. Try finding an executive who wants to work somewhere where they hit singles...he has an MBA you know, he swings for the fences every time. You are vastly overestimating, ironically, the intelligence of most people who work in companies (I worked in equity research for a while...Buffett's dictum of a company that could be run by a ham sandwich has much wisdom).
You're essentially implying that companies like FAANG can get by just fine, even if they hired "average" programmers, as opposed to "exceptional" ones. If this were the case, they wouldn't need to pay anyone 250-350k compensation either - they can just hire some average programmer for 70k and call it a day. Or better yet, hire someone in a country with much lower COL, pay them 30k, and everyone walks away happy.
I don't think this is true, for the simple reason that companies are far too greedy to pay people 200k a year, unless they really need to. Do you honestly think that a company like Amazon is going to spend hundreds of thousands of dollars on someone, if they can get someone else for a fraction of that? Maybe I'm wrong and one day, some startup will grow to be a unicorn while paying their developers sweatshop rates. I'll believe it when I see it.