As far as I know this is indeed 'normal'/necessary.
It's just that you have to do something to tell TG how many shader nodes
and for which parts it has to create for your model.
But assigning in maya or elsewhere only means you have to simply assign
a shader to any group of polys you want to have separate shader.
Only assign it to that group,nothing else
required.You can use copies of that
shader as long as they are named differenty (like Phong01,Phong02 etc) and you
don't use UVs.With UVs you need the corresponding shader (in maya) of course.
Couldn't try with fbx so far,as I don't a fbx2014 reading app to test with.
TG doesn't import geometry via fbx as of now.
I would prepare a bit more detailed explanations on the shader stuff for the
other thread,if there's interest.