Reports that include grouping are exported differently from Java UI than from the uCMDB Browser.
Support confirmed that current Browser behavior is implemented that way. It won't copy and paste data of 1st level into each line of 2nd level (aka how applet ui works right now).
The idea suggested is that the browser should produces the exports the same way as the Java UI.
Well, in the list I had, the status of this ER was "Waiting for Votes"
However, it appears to be something going on with this Idea Exchange tool, as this particular instance of the ER was NEVER in Accepted status. However, another ER with exactly the same name and details (/it_ops_mgt/ucmdb/i/cms_idea/csv-exports-should-work-the-same-for-java-ui-and-ucmdb-browser) shows that it was in "Accepted" status on the date you mention.
And when I updated this one, the other one sync'd up to be the same
I have escalated this to internal support to see what's going on.