Can't change AdminSearchResultRows config option in plugin config file


we have an internal plugin where we have a etc/ file
to change some config options (similar to [1]).

I now wanted to change AdminSearchResultRows [2] from 50 to 100 and
copied the option from etc/ to my plugin
etc/ file and changed the values.

After a webserver restart Admin/Tools/Configuration.html reported as
source for AdminSearchResultRows my file but the
values are still 50 instead of 100. And Admin/Queues/ shows only 50
queues per page.

If I copy the AdminSearchResultRows option from etc/RT_Config to
etc/ and change there the values,
Admin/Tools/Configuration.html reports the changed values and
Admin/Queues/ shows 100 queues per page.

So changing AdminSearchResultRows works in etc/ but not
in a plugin etc/* file.
Any ideas for this funny behavior?