A big part of a dentist's income is yield from educational investment. The education and training is the capital.
In which case, yes, owning a plumbing business is closer to capital than working at one, which is in turn closer than doing unskilled manual labour on a job site. And on the other end, maybe owning an Airbnb which you clean yourself is closer to labour than owning a portfolio of ETFs.
Something I always intend to do and regularly find myself falling short of! Thank you, your interpretation makes sense (as most interpretations seeking nuance do)
> You're a plumber with years of training? Face the wall, capitalist pig.