Jim Austin is absolutely right. One major point of this award is that preparing an application requires applicants to engage in overt career planning and negotiations with their postdoctoral mentors.
Major components of the application include the mentors' statements and the applicant's career development statement - study sections pay very close attention to these. By requiring these components, the application stimulates meaningful discussions between postdocs and PIs about how to develop independent projects, how to contribute to the PI's lab in ways beyond generating data for his current projects, and how to develop an independent identity as an innovative scientist. For me, preparing an application provided a framework for these discussions, which involved plenty of constructive criticism and lots of practical planning. It also provided a framework for networking in the field, and for turning collaborations into formal co-mentorships, which became incredibly useful in my search for a faculty position.
One thing - I have some friends whose K99/R00 proposals were rejected because they too closely hewed to their PIs' work - these guys still got faculty positions and quickly turned those proposals around into successful R01 applications. While they did not get K99/R00s, they definitely benefited from the experience of preparing R-type grants while they were still postdocs.