V4, V3, V2, the EF figures, the former Poser figures, any and all of that through all Poser's history....
All of those figures are nothing more than 3D meshes. In Poser of course, they're rigged, some well-rigged, some not so good.
But there's no reason at all for anyone to simply have to deal with it. To say that V4 (or any of them) doesn't bend like a real person is a moot point, since the bending is only limited by the way the geometry and bones are designed, any and all of which can be altered by anyone with the knowledge and the persistence.
My hypothetical "PoserUltra" would make all that easier and allow one to do it within Poser itself, rather than other apps, plus allow for new figures to be set up more easily.