I have created this account for the very purpose of contacting NT Entertainment and therefore I am new to this website and/or its way of functioning.
I have experimented to see if the bias is the case and it seems that after editing the vmt to say it is "LightmappedGeneric" it proceeds to import that material but none other. I want to know if you are aware of this bug involving that of discrimination from non "LightmappedGeneric" vmts.
EDIT: I have done this with all the vmts in the folder. Now the plugin creates a material for them.
I have no idea what to tell you, except that I can't reproduce your problem at all.
I just ran a test with a cable materials directory (so just "SplineRope" and a "$basetexture" field), and those all imported fine without needing to change or edit anything in the VMTs, so I have no idea what was going on on your machine. Any unknown types should default to the LightmappedGeneric handler anyway...