I don't think that's it? "Org chart" describes both charts that identify particular people and also charts that describe the larger organization[1]. When Facebook says they are going to hire 3000 engineers, they are adding 3000 people to the Facebook organization. Even if they don't know what division / project / team / etc those people will end up in.

Edit: Probably a better thing to say is - even if I was using org chart wrong, I don't see how it would make a difference. Hiring N people that fit a set of requirements is seeking to fill N positions.

[1] https://en.wikipedia.org/wiki/Organizational_chart has examples of both. You could imagine the organization chart of Tabulating Machine Co. including headcounts for each division.