No, you did the right change. Strange that it generates qualifier instead of density. And you also added a line for when the device is in portscape instead of landscape?
<splash src="res/android/screen-ldpi-landscape.png" density="port-ldpi"/>
Regards,
Ronald
For completeness, contacted Mendix and this was recognized as a bug and will be changed.
For now you could change the attribute to density yourself.