[Jeff Brown] “Most people don’t even notice lip sync that is off by 2 frames.”
I suspect you are correct, especially those folks who watch SD video stretched across a wide screen TV.
But I guarantee that every editor here can detect out of sync lips by much less than one frame and that is why you can change the time display mode of the timeline to Audio Units. Then zoom way, way in and you can move the audio track by one sample (1/48,000 of a sec).
(the menu at the upper/right corner of the timeline)