"Unbeknownst to Raskin, Jobs had his own reasons for visiting PARC: Xerox's venture capital arm had recently made an investment in Apple, and had agreed to show Apple what was going on in its lab."

I think this is kind of the point they make in Steve Jobs bio as well. Xerox allowed Apple to use some of the concepts in the lab because they were investors in the company. Also, if I recall correctly, Apple engineers went a little farther in the window metaphor, allowing, for example, to overlap and stack windows, something XEROX wasn't able or willing to do.