Many people who are filthy rich by being corporate asslickers, the human trash that get paid huge amounts for manipulating the masses, and other similar people don't own anything yet they can hardly be called part of the proletariat.
Are they petty bourgeoisie or an exception of the working class that works against it?
They are labor in the work of disciplining the labor sector. So in narrow definition - pmc
In same way as cops are working class in that they receive money for their labor, but their function is not to produce stuff but discipline the masses, their product is only useful for the bourgeoisie
"PMC" is a liberal term, not a Marxist term, in my opinion
It's not marxist in the strictest sense, but like usa labor force has 12 million working in manufacturing and 22 million in professional/business services. (I'm obviously overdramatizing, cause there are logistics/construction/healthcare/hospitality as well, which will bring worker number to something like 70 million)
Its a whole separate worker group, whose services are to make bourgeoisie more money/comply with the state to not lose money. If i were reaching for a term mentioned in marx i would call them lumpen (professionalized) proles