Import rotation of 3DS Max files differs between single mesh vs multiple submeshes...

When importing a single mesh, the import preserves 3DS Max's axes (in which Z is up). The mesh effectively comes in "sideways" and Unity auto-corrects this by rotating instances by -90 around X when you drag them into the scene.

If you have more than one mesh in the 3DS file, however, the behaviour changes; Unity automatically imports each mesh as a child of a non-meshed root transform. When you drag an instance into the scene, there is no rotation applied to the root transform; rather, each of the child nodes is individually rotated by -90 around X instead. This seems to be a far more useful behaviour, as it preserves the semantic "up" direction between applications and gives your instance a clean starting rotation.

My question is whether there's any way to force Unity to treat single meshes in the way, such that it creates the non-meshed root transform parent automatically? It would save a bit of grunt work in having to create parents manually...