Comentário oficial
Master Tempo doesn't have anything to do with the tempo or sync; that's just a setting that locks the "pitch" of the audio (the key) so it doesn't sound altered when you speed it up or slow it down.
The problem you had with the pitch itself was when you are sync'd, you can ONLY move the pitch fader on the master deck for it to affect both decks. If you want to change the pitch for the SLAVE deck, either switch the master or disable the sync function.