The only inaccuracies we spotted were ones where a kid graduated from BS planning to attend one school and got off a WL in the summer and changed plans. But right up to graduation day, the students kept the CCs apprised.
This is just a guess, but I think that the students going through the process appreciate having good data, and at least at out school, always had a strong desire to be good community members, so felt that they owed good data to the classes behind them as payment for the good data the classes before had left them. So while the CCs mandated it, compliance was no problem.