Question Unity Blend Shape Normals Broken

After doing some searching, it seems like the current state of Unity at all versions is that Calculate BlendShape normals is broken. Atleast, for some people.
My guess is that these people, like me are using BlendShapes where the angle may exceed the maximum Smoothing Angle of 180, though I could be wrong about that. This assumption is just based on the testing I've done where my more extreme blendshapes for joints (like the knee at 155 degrees of motion) only have distorted normals near the far end of their ranges and are otherwise functional.

I'd like find out if there's a way around this issue as the only *solutions* that I could find are to;

• use the Import Normals option which is redundant if you don't have normals in the FBX (I don't think you can export/bake blendshape normals into the fbx if you use blender).
• use the "legacy blend shape normals" option.

Both of the above solutions arn't really solutions, they hide the issue by effectively replacing all blendshape normals with the base normal. Therefore, blendshapes have no visible effect on the normals which in my use case is an issue and largely makes the more subtle blendshapes practically useless.

Is there an actual solution to this any one is aware of? Or possibly a way for me to alter the smoothing angle logic used on import and see if giving the algorithm an unclamped smoothing angle helps the problem?

 

Bump. Is this on the radar, does it need to be filed as a bug? Observed on both 2020.3 LTS and 2021.3.18f1.

 

I've been getting similar behaviours over the years, and recently I came upon this (which does not seem to work on my end):

https://forum.unity.com/threads/blend-shapes-changing-vertex-normals.632230/

But it's been happening since forever, it seems. Setting the blendshape normals to "None" is not an option, because the shading of the volumes does not update with their deformation.