Creating Material Assets with Metallic / Smoothness Channels

Hey there, I've been struggling with what seems to be a simple problem, and I'm hoping the answer is just as simple.
I've been working on a tool to merge texture sets and automatically create a new material asset for those texture sets, and everything works so far, aside from the metallic smoothness channel. After looking around yesterday, I read that you need to use EnableKeyword to indicate shader variants.

I've broken down a small part of my code to give an overvierw:

Code (CSharp):

1. Texture2D MetallicGlossMap = (Texture2D)AssetDatabase.LoadAssetAtPath("/PathOf/RecentlySavedPNGAsset.png", typeof(Texture2D));  
2.  
3. Material newMaterial = new Material(Shader.Find("Standard"));
4.  
5. // Enable the reqired Shader Variants
6. newMaterial.EnableKeyword ("_METALLICGLOSSMAP");
7. newMaterial.EnableKeyword ("_NORMALMAP");  
8. newMaterial.EnableKeyword ("_DETAIL_MULX2");
9. newMaterial.EnableKeyword ("_PARALLAXMAP");  
10.  
11. newMaterial.SetTexture ("_MetallicGlossMap",MetallicGlossMap);
12.  
13. // And obviously the other required Textures.
14. //newMaterial.SetTexture ("_BumpMap",..Normal Map...);
15. //newMaterial.SetTexture ("_EmissionMap",...Emission Map...);
16.  
17. AssetDatabase.CreateAsset (newMaterial,"/PathOfTheMaterial.mat");
18. AssetDatabase.ImportAsset("/PathOfTheMaterial.mat", ImportAssetOptions.ForceUpdate);

The result is a newly created .mat file with every channel I've needed so far, with exception of metallic smoothness. on first Inspection using debug mode, I do see the shader keywords applied as I've illustrated in the screenshot attached, however, when I use the normal inspector and return to debug inspector, those keywords have been removed.

If anyone has any pointers as to what I am doing wrong, I'd really appreciate it.

 

I suppose I should mention that I am using Unity 5.6.3f1