This excerpt tells us that the exploitation of productive labor on a large scale requires a "real army" to prevent workers from taking control due to the opposing interests between the capitalist and laborer. The excerpt tells us that this is a "special kind" of wage-labourer ie not a productive labourer, not working class. The excerpt tells use that this kind of laborer is "faux frais of production", meaning that this person does not add value to production. The excerpt tells us that the role is the person is to control the antagonism of interests between the capitalist and working class.

The “real army” in this excerpt is metaphorical and Marx is clearly talking about managers and supervisors. As I mentioned in a different part of the thread this has echoes of that barista debate from last year because of people using the distinction of productive vs non productive work as their estimation of whether or not someone is in the working class.

I am willing to accept that managers, supervisors, cops, and people who are generally on the side of the bourgeoisie as part of their occupation are not proletarian - but it makes me wonder what they are? Simply “a special kind” of wage laborer? That’s kind of an unsatisfactory description.

I think Engels provides a useful framing for this debate and for how we can think about working classes in current year. I also don't think this actually disagrees with what you're saying.

What is the proletariat?

The proletariat is that class in society which lives entirely from the sale of its labor and does not draw profit from any kind of capital; whose weal and woe, whose life and death, whose sole existence depends on the demand for labor – hence, on the changing state of business, on the vagaries of unbridled competition. The proletariat, or the class of proletarians, is, in a word, the working class of the 19th century

Proletarians, then, have not always existed?

No. There have always been poor and working classes; and the working class have mostly been poor. But there have not always been workers and poor people living under conditions as they are today; in other words, there have not always been proletarians, any more than there has always been free unbridled competitions.

So then under this framework we can consider proletarians a particular kind of worker with a relatively specific definition and actually do not make up the majority of the workers of western economies. However from this exerpt we can conclude that one does not actually need to be proletarian to be working class. So I think a lot of us (including me) are conflating the two and causing unnecessary confusion and we should regard the proletariat as a subset of the broader working class.