As others have pointed out, 500ms is huge for some applications. But when the use case is selecting a song from a playlist, starting to hear the track 1 second later is totally fine. It's often preferable to a stream with <30ms latency that drops a buffer every once in a while.

I'd guess the latency comes from generous buffer sizes that keep playback rock solid even though this does TCP, potentially over somewhat flaky WiFi. Keeping separate speakers synched within 1ms is pretty good — you'll cause a greater variation than that just by moving your head to look at the phone with the playlist :)