LDraw part 118091p looks fine in Part Designer but imports into Studio with extra geo

[Orion Pobursky]

Not really.
Eyesight is a modified Blender 2.79/2.80.  It’s not a clean release version of Blender that was then modified, it’s one intermediary version of Blender that was modified, then updated to a new work version of Blender and modified again (and maybe even that but several times).
There’s much less work to redevelop something from Blender than to try to adapt Eyesight.
Plus, Blender 2.80 is from 2018, that’s an eternity of enhancements since.
Worse, Eyesight uses the Collada format, which is deprecated because unmaintened for years.
Double worse, the Collada format in Eyesight/Studio has been modified (without any documentation).
TL;DR: it’s a nightmare.

(Note that if it took so long for Eyesight to be open-sourced, it’s because it did not belong to BrickLink.  It had been subcontracted and it took BL some time to eventually buy all the rights.  And they made it open source because they don’t have the resources to do more than add or correct colours….

As I suspected, it would be better to just develop for Cycles directly.  See my other thread:
https://forums.ldraw.org/thread-29616.html