Interesting comparison. You’re right. The primary difference I can think of is the training to quickly become an expert in a different topic.
I know plenty of PhD students accepting jobs in unrelated fields and quickly becoming the local expert in that topic.
While possible, it’s far more difficult for a machinist to suddenly become an expert car mechanic like this.
Kids (kid being someone from 16 to 30 without children of their own, ideally also without substance abuse problem and a home they can sleep in without fear of being assaulted) have nearly infinite energy, capacity to absorb (physical) abuse, and often the focus to learn esoteric subjects, if they're interested in the subject.
So I would fully expect a large fraction of bored kids to potentially become expert car mechanics, or tree pruners, algebraic geometers, hadoop experts, air conditioning duct builders, etc, if given access, mentorship, opportunity, recognition, and compensation.
You seem to have missed my point though, it was about switching tracks to become an expert in a new thing. A random physics PhD grad might not have a burning passion for fintech, for example but still becomes an expert after three months in the job because of the sheer amount of rigorous training.
Now, how much of this is actual expertise and how much wealth extraction, I really don't know.