Occupational heritability will also be boosted by the "company town" effect. I feel that might be a confounding factor in their analysis for many working class occupations.
If you are raised in a town with a big steel plant or textile mill and you don't leave, you're likely to inherit a parent's job by default...
I grew up in a fishing village - I've got something like 15 generations of ancestors who worked (and quite often died) working at sea. I'm very glad to have a job inside mostly sitting at a desk.
It's confounding in the sense that if a child has the same job as their parent, we assume that parental influence may have had something to do with it. Which it probably does, in a lot of occupations. But when the "company town" effect occurs, it's not necessarily because of parental influence.
It's merely a lack of other options.
If you are raised in a town with a big steel plant or textile mill and you don't leave, you're likely to inherit a parent's job by default...