Bringing in FBX is combining meshes and materials??

Hi, I'm new to Substance Painter and I seem to have confused myself. I have an FBX with an empty/null root and contained in the root are individual meshes and materials for a wall and its door frame.

|-Corridor

  |---Wall

  |---DoorFrame

When I import into Substance Painter all I see is a single combined view and a Texture Set with a number (1001) and a single material. I was expecting to see the basically same mesh topology and the two materials. Am I importing it incorrectly or is this the expected behaviour?