ID 372020 - Highlights in AVP with materials set to "Principled" are incorrect relative to render

Problem summary
Highlights in AVP with materials set to "Principled" are incorrect relative to render. These highlights do not appear correct relative to Physically based materials or the render of the principled material.

Customer reported version
modo.12.1v1

Customer reported platform
windows10

Steps to reproduce
1) Open Modo.
2) Open the provided scene.
3) Change the viewport style to "Advanced."
4) Press "f9" to render the scene.
Result: Right sphere (set to the principled material) highlights do not approximate the highlights in the render.

Workaround
Unknown. 

Reproduced by support
This bug has been reproduced in:
12.1v2 - Windows 10
12.1v1 - Windows 10, OSX 10.13.5

Unable to reproduce bug in:
12.0v1 - Windows 10, OSX 10.13.5

Earliest version tested
12.0v1 - Windows 10, OSX 10.13.5 - This issue no longer appears in this version and has regressed

Expected behaviour
Advanced viewports should approximate specular highlights in the render across each material shading model.

Actual behaviour
The Principled shading model does not show correctly approximated highlights.