I think that's a pretty plausible idea, but it has one flaw. If it was true, then companies would be announcing this as the cause. They'd be shouting it from the rooftop if they had any data to support it.
There's very different metrics when dealing with a team of mostly mid and senior devs at a small shop that can carefully mentor / manage their handful of junior devs ... and one that is working on the scale that Amazon is working on.
The org with a few teams and 100 devs total works and mentors differently than how Amazon operates.
