So the people who have amazing LSAT scores and GPA's that they admit will probably go to a better ranking school unless they are really committed to Public Interest law
You hit the nail on the head as to why the wait is so long. They no doubt have hundreds of accepted applicants that are in a continuous cycle of rejecting their offer, which leaves them with additional slots to offer to someone else. So long as that process continues (determined by the total number of applicants they have to review), the longer the wait for us. Although its long and is capable of driving the sanity out of an individual, it's also very fair and works to the advantage of those who really want to go (like me!!!).
how low would your LSAT score have to be to be admitted into this pipeline for justice program?
Good question - it's probably a combination of a poor LSAT score and poor GPA, but the specifics I don't know. It's all very subjective as you've probably realized by now - if the individual has a great public service record but a less-than-median LSAT and GPA, they would probably be candidates for the program.