Undocumented GDAL 2.3.0 CSV output geometry column name change breaks WPSOgrTest

On debian sid gdal-bin 2.3.0+dfsg-1 amd64:

Failure started after upgrade from GDAL 2.2.4 to GDAL 2.3.0 on Debian sid when processing a GML file with a geometry property called `geometry`. The output CSV geometry column name changed from WKT to geometry:

Comparison with Ubuntu Bionic:

GEOMETRY=AS_WKT is documented to output a geometry column WKT by default.