This strikes me as a narrative that's much easier to state and nod along to, than to demonstrate. Companies are ruthless about cutting fat. They have departments dedicated to isolating unnecessary employees and firing them. Beurocracy is inefficient, but it's rarely completely wrong. It's very easy to tell when an employee is contributing nothing, even for a monolith.
What I think actually happens is that companies hire more people for a particular role than they need, because load balancing is difficult, or they have a structure that extracts productivity from the workforce in a way that's inefficient. But that's not the same as outright non-productivity. Those people are not useless - they're still productive, they just provide suboptimal (and maybe negative) return on investment.
> For example, jobs may be created as a placeholder for otherwise unused staffing budget.
I don't think it works like that. They may invest the excess staffing budget in a productive worker they otherwise wouldn't have hired, but that's not the same as hiring someone who provides no benefit. The return that employee brings may even be negative but it's very, very unlikely to be -100%.