Grouping lost upon .dae file import to SketchUp

I am playing with .dae file import and encountered the issue as in the following test scenario:

  1. In a new SU file, I create two cubes and make each of them a group.
  2. I export the 3D model to a .dae file.
  3. I re-import the .dae file to a new SU file.
  4. The imported cubes appear closed in a common container so that they move together, preserving their relative position. I can apply ‘Edit Component’ or ‘Explode’ to the container.
  5. After ‘Explode’ executed on the container, the cubes are no longer groups, but collections of separate faces and edges.

Is there a way to avoid this ungrouping? In other words, is there a way to:
a. keep the group definitions in .dae files?
b. make SU maintain those definitions when importing?

Thank you in advance for any help.