Actually not uncommon.  Voice syncing used to be done right on the media (35mm film, video tape).  That wasn't problem when the voice amplifier delays were known and very short, and the video was processed at the speed of light (projectors), or at the speed of video amplifiers where the images were created line by line at very fast rates.  The read head picked up the voice track, and while I don't know the details of projection equipment for 35mm film, adjusting the position of the head, and adding signal delay could be used to sync audio and video.    Now we have various recording media encoded digitally, and the equipment used doesn't always account for variances in audio / video syncing from those sources.  Depending on the recording media, the offset can be significant.  We also have the issue of digitally processed video, which can induce a significant latency in the video track, which is offset by delaying the audio stream. Some TVs allow you to adjust that delay to sync the audio and video for the typical programs you watch.  But it still may not match for all sources or broadcasts.