Messed up Substance Painter import

Development Asset Creation
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1

I selected File → Export textures and picked the Unreal Engine 4 (Packed) template in Substance Painter.

This is what my model looks like in Substance vs Unreal.

Certain parts are completely blank in Unreal.

neolithic-head-substance
neolithic-head-substance1206×1420 108 KB

neolithic-head-3D
neolithic-head-3D1080×1156 188 KB

What did I mess up here?

2

I re-exported this as a glb and imported as a glb and it works fine. I had followed a tutorial that used the Unreal Engine 4 (Packed) template. What is the benefit of using this template? With that template I had to manually link up the different texture files to the model. The glb just works. Why would I ever not use glb?