That's fair, I do acknowledge that the PM role varies greatly between companies (and often within companies). For example at my company PMs would never make a UI mockup, they would basically be the bridge between designers, management, customers, and engineers when it comes to UI. But if you aren't requiring your PMs to be technical, I mean the sheer amount of people qualified to do that job (even with stipulations such as "knows design") is a lot greater than the set of people who are qualified engineers.

But I also think it's ignorant to say that companies just want folks proficient in specific languages. That might be true for people without much experience but in most cases beyond that (which pay well) people are looking for deep technical understanding of a specific technology (e.g. deep learning) or a specific problem (e.g. scaling large web services).