I agree with them, it was not designed for "painting" neither was photoshop, but the advantage to it being open source is that someone can (and rest assured some one will!) fork it and make something like GIMP Paint.
However both of you are focusing on that, read further down and you get this:
Quote:
the freedom to create
imagine users almost in trance while they are creating, they know what they are doing, but also react to what they see on the canvas in a very tight feedback loop; the tools in GIMP follow these users to wherever they want to go, even if this is way outside the intended use of a tool or algorithm
They may be saying that "painting" is secondary to the focus, but they still push for people to use gimp in unexpected ways and that it is what "painting" with Gimp is! Don't just dwell on the fact that it is
NOT dedicated to painting, but instead that they even acknowledge that there are GIMP "Painters" out there and may eventually bring in more aspects of "painting". Remember that they did bring more presets, brushes, dynamics and such from GIMP Painter.