Trying to understand Bounding/Alignment Box Behavior

[doone]

Hello Everyone,
I have searched to find an explanation on why the Bounding or Alignment box automatically enlarges when converting a simple rectangle into a Group and have not been able to do so.   Is there a way to force the Bounding box to be the same size as the rectangle?  Here's an example of the behavior I am seeing:
Kind Regards,
Lorna