Why is dialogue usually mixed to the centre even when the actor is off to one side, and what does that imply for placing generated dialogue and effects in stereo or surround?

Problem: deciding where to pan AI-voiced or dubbed dialogue versus effects and music. Conditions: stereo or surround mixes with picture. Method (Murch's observation): in almost all stereo films of the previous 25 years dialogue is placed in the centre regardless of the actor's screen position, yet audiences and mixers still believe the voices come from the actors; effects such as car pass-bys get full stereo or multichannel treatment. He explains this by saying that while the brain is busy decoding language it lets the image 'steer' the apparent source, whereas the less linguistic a sound is, the more its spatial location matters. General rule he states: the warmer (more embodied) the sound the more it gets a stereo/multitrack treatment; the cooler (more encoded) the more it is placed in the centre. Early 1950s experiments moving dialogue around the screen were abandoned as 'artificial'. Use (inference): keep AI dialogue and dub lines centred (or head-locked in 360/VR, see the spatial-audio findings), spend spatial effort on effects, ambience and music, and make sure picture, not panning, tells the viewer who is speaking. Failure modes: panning dialogue with the actor in a way that exaggerates cut-to-cut jumps. Limitations: observation, 2005 vintage; cinema convention rather than a physical law. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Convention reasoning; no test data. Extension to VR/head-locked placement is my inference from the YouTube head-locked layout. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://transom.org/2005/walter-murch",
      "note": "cited at https://transom.org/2005/walter-murch/; Dense Clarity - Clear Density; Dense Clarity - Clear Density; Dense Clarity - Clear Density"
    },
    {
      "url": "https://transom.org/2005/walter-murch/",
      "note": "observed URL (dated/alias form of the cited catalogue source; canonical identity retained)"
    }
  ]
}