Interesting. The question is whether that documentation includes details on how to drive the printer at high quality. I suspect not.
The iP4000 driver in Gutenprint 5.0.0 cannot drive an iP4200, which disproves the theory that the iP4000 driver should work for the whole lot. As I mentioned above, the current cvs version is already fixed to work with the iP4200 as well, but it does not work with an iP4300.