Characters in Half Life 2 look directly at the player when talking to him, but that is not possible when using motion-captured animation. John is not really a technical guy, but he's got his info from developers close to the project. According to John Lowrie, a voice actor who has worked on several Valve games including DOTA 2, Left 4 Dead, Half Life 2 and Team Fortress 2, one of the main reasons behind half Life 3 delay is that Valve is waiting for better motion capture technology.
