Using explicit normals works with meshes coming out of Maya as well. I bake normals in Maya (AO in Xnormal) with all UV island edges hard, export as .FBX, then import into Unreal with explicit normals, and I get clean results.
So qualified mode on its own is unrelated to unreal. The reason you need to enable it in max is that the exporter uses whatever tangents are being displayed and in max pre-hotfix 4 the viewport tangent basis didn't match what the render to texture was using. With this workflow you are just packaging the tangents into the…