One of the worst cognitive biases which humans suffer from is the belief that observations about individual people can be generalized. How much faulty thinking, including racism and sexism, stems from this simple error? An extension of this common mistake is thinking of people as interchangeable, or fungible, when planning work - pretending who does the work doesn’t matter.
A pattern I've repeatedly seen is companies will plan out the next few quarters of work and then assign some number of people, one person for one quarter to a project, two people for three quarters to another, etc. This process enables executives to make decisions about costs, priorities and project funding. This works for it's purpose, however, the roadmap creation and review process perpetuates the fiction that people are interchangeable, that people can be generically abstracted over.