This is not a common way of speaking anymore, IMO. When I read "all the developers are men", I didn't understand what you meant at all. I thought maybe you were making some kind of ironic joke about sexism. I did get what you meant after re-reading of course, but "All people are men" sounds very archaic to me, like something out of Tolkien.

Usually when we want to talk about humans as a species or whatever, we now use the word "human."