OMP modify_reprot not showing results

Hi,
I’m trying to add a comment to my report following the API here:
https://docs.greenbone.net/API/OMP/omp-7.0.html#command_modify_report

but it does not seem to actually modify the report:

    omp --xml="<modify_report report_id=\"5414b28d-849e-466e-a781-1548f2e1081a\"><comment>test</comment></modify_report>"
    <modify_report_response status_text="OK" status="200"></modify_report_response>
    omp --xml="<get_reports report_id=\"5414b28d-849e-466e-a781-1548f2e1081a\"/>"
    <get_reports_response status_text="OK" status="200"><report id="5414b28d-849e-466e-a781-1548f2e1081a" format_id="a994b278-1f62-11e1-96ac-406186ea4fc5" extension="xml" type="scan" content_type="text/xml"><owner><name>admin</name></owner><name>2019-09-19T12:40:39+02:00</name><comment></comment><creation_time>2019[...]

The comment field remains empty. What am I missing here?

Please note that the OMP protocol itself, the OMP API documentation as well as the omp command line client are deprecated.

The replacements are (See e.g. Omp library as well):

https://docs.greenbone.net/API/GMP/gmp-7.0.html#command_modify_report