StandardMaterial Sheen does not work with Specular workflow

[Maksims]

If a material uses specular workflow (useMetalness is false), then sheen will be ignored.

[mvaligursky]

Possibly this is the problem?

https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_sheen/README.md

KHR_materials_sheen

Exclusions
This extension must not be used on a material that also uses KHR_materials_pbrSpecularGlossiness.
This extension must not be used on a material that also uses KHR_materials_unlit.

[Maksims]

Should the engine do same limitation? It kinda works, if you specify sheen, end then tick back and forth the useMetalness, then it applies it in Editor.

Would be great to have it regardless of specular/metalness workflow.