Import course in Admin Backend

I have been working in edx-platform since a long duration of time.
When we import a course from the CMS there is an issue I met while importing that.
When we already have any section/unit in Course but is not is the course that we are importing these course are kept in mongodb as it is the one that are same are replaced. 
I just want to know if that was kept like that or is really a bug.
If that is a bug I would suggest to update the revision counter to something other than "draft" or "null" that can help recognizing.

Thanks and Regards
Chand Prakash