The Acoustic Id Database is run by AmpliFIND, not all those tracks are in the Musicbrainz database , and even if they are they don’t neccessarily have a link via the acoustic id because somebody has to say ‘This acoustic id maps to this Musicbrainz id’. Thats why I urge you to use Action:Remote Correct:Submit Musicbrainz/PUID pairs within Jaikoz to improve the database and thats just one reason why we use metadata matching as well as fingerprinting matching.
Currently Musicbrainz contains 10,348,616 tracks but only 5,854,341 acoustic ids (about half the tracks)