And then move person with 4 years of work experience slightly out their comfort zone. Say working on designing locks, to working on designing engines.
The mechanical engineer would have a better time. It's one of the reasons vocational/on-the-job educated people end up with lower wages; generally educated people can go where the money is.
People with good contacts, are good at networking, good at marketing, and interested in money go where the money is. A history of creating business value, and a bunch of people who know about it, are a lot better than a general education.
This is slightly complicated by the fact that people going to well-known colleges get a head start on the network. A decent education on its own has more dubious value. Most companies want experience. I know that when I evaluate someone, relevant experience is way more important than if or where they went to college.
That's the point. Relevant experience. Jobs are very specialised. If you have one mechanical engineering job, you might not have much knowledge to transfer to another type of mechanical job.
That's what a general education in the subject is for.
The mechanical engineer would have a better time. It's one of the reasons vocational/on-the-job educated people end up with lower wages; generally educated people can go where the money is.