Looking at the MySQL tables, it seems that policies only hold information about the policy entry itself, rather than the logs / statuses. There is a table called logs which appears to hold the policy log entries which might hold the info you're looking for but there doesn't appear to be any API options for it.
I have looked at accessing the MySQL DB directly before and much prefer using APIs where possible. The main difficulty, apart from not being officially supported, was correlating data from one table to another. Information for individual items you can see in the JSS web interface can be spread over lots of different MySQL tables with no obvious way to correlate them.
