Yes it is a myth. Turnover was at 9 months average per employee on the floor, and there were so many car companies in Detroit that it was easy for a skilled worker to quit and find work somewhere else for the same or better pay. So Ford raised wages and then held employees to a high standard of conduct. He had people inspect workers homes for alcohol use or signs of bad behavior in the eyes of Henry Ford. "Wheels for the World" is an excellent book about Ford's early years.
You can see the same thing happening now in Shenzhen. Workers know that they can get a job easily if they have some experience, so many don't return to work after a holiday. Wages have also gone up rapidly there. I just returned from a month in Chana and managed to tour a couple of factories while I was there. The complaint from the factory owners was skilled labor and the price they had to pay to retain them.