Variant Stripping: Shader keywords are invalid outside of the Editor

I'm trying to strip Unity Post Process's shaders. To do so, I have a list of unwanted keyword and I strip incoming variants using this list in a IPreprocessShaders.

It works perfectly when I build from the editor, I go from about 5000 variants for Uber Shader to about 90 variants.

But when I build from the command line nothing is stripped at all because the list of unwanted keywords is somehow empty (it's keywords inside the list that are empty). In fact, when I check their validity before stripping the variants, they are all invalid if the build is being run from the command line. This is also true if I add shaders using those keywords inside the Preloaded Shaders list of Graphic Settings.

The problem is that if a keyword is invalid, passing it to ShaderKeywordSet::IsEnabled will always return false.

Here is the code that checks keywords validity.

  class ShaderVariantPostFXStripper : IPreprocessShaders
     {
         // Every keywords we don't want to be compiled.
         private ShaderKeyword[] m_ForbidenKeywords;

         public ShaderVariantPostFXStripper()
         {
             // Create keywords.
             m_ForbidenKeywords = new ShaderKeyword[] {
                 new ShaderKeyword("GRAIN"),
                 new ShaderKeyword("DITHERING"),
                 new ShaderKeyword("VIGNETTE_MASKED"),
                 new ShaderKeyword("BLOOM_LENS_DIRT"),
                 new ShaderKeyword("USER_LUT"),
                 new ShaderKeyword("DEPTH_OF_FIELD"),
                 new ShaderKeyword("DEPTH_OF_FIELD_COC_VIEW")
             };
    
             for (int j = 0, l = m_ForbidenKeywords.Length; j < l; ++j)
             {
                 if (!m_ForbidenKeywords[j].IsValid())
                     Debug.LogError("[POSTFX Shader Stripper] Invalid shader keyword at index " + j);
             }
         }
 ...

Do you have an idea of where I should take a look to fix this problem ? Or do you think this is a bug ?

Thanks in advance.