This person asserts that headcount is a measure of success, but I suspect they are confused about headcount being a proxy for production volume, which would be a closer measure for success. Every healthy team has more work than they have people available, they all want more people because they wanted to get more work done.

Teams that would allow engineers to idle should be the exception and not the norm. I am not sure extrapolating the experience from such a team would produce an accurate image of a large company.