Have you tried using the support|self support option to request that cache code?
Alternatively it may be that one of the people who have voted for the cache have opted not to share their information with third party apis (such as project-gc) and therefore project-gc doesn't have the information available - I don't know the implementation details to know how that would show up in the results but could imagine it might see the total number of finds but not get to see their vote.