This makes a lot more sense than the idea the engineers are too incompetent to make the radio overlay match up with the video. Now I am wondering whether the situation is simply that the AV engineers working local TV and audio engineers working local radio on a game broadcast are two different sets of professionals working independently for different companies and are beholden to their companies’ different mandates, and that there’s a third set of engineers (?) working for MLB who are responsible only for making the radio audio available with the video as an option for MLB.tv subscribers to listen to.
If this is truly the situation, it might explain why there are other broadcasts that experience this timing mismatch between radio overlay and video, and others that do not: some teams’ radio audio or TV AV engineers may engage in this compression tactic as a way to shoehorn a full pod of commercials in, while others may not. It would also seem to explain how the overlay/video mismatch can be substantial in one part of the broadcast, off by five or even ten seconds, while matched up perfectly in another part of the broadcast.