First of all let me clear out generating a report pdf is different from excel.
The Repeating Frame and boxes,lines etc., used in your reports plays a vital role in excel.
Because, the fields in the reports are segmented into XL cells and displayed as the output.
For Better results in excel...Follow the below instructions,
--Make your repeating frame and main frame visible (don't put 'NO_LINE') for any frames,
--Don't leave any unnecessary spaces in reports between fields,frames etc.,
--Then run your report.
It will work fine,
The order of the columns in the excel export is determined by the order of the fields in the query that is present in the data model. If you check the property pallate of the data field there you can find a label as XM Tag there check whether the name is there or not . If the XML tag i snull then you will not be getting the XML tag