One possible reason that your colleague got black text and you didn't, if indeed you used the exact same export settings, could be that you are using different CMYK working spaces.

If his matches the original document there would be no conversion. If yours does not there's a possibility that the colors were converted to your space when the document was opened, depending on your color settings and conversion policies. That could be confirmed before export in the separations preview.

If your text appears as black only in the preview, then a mismatch between document and destination spaces would yield rich black text unless you leave colors unchanged.

Peter