GeoServer WFS 2.0 CSV output multiple features/typeNames

Question

I'm setting up an export function so that users may download data from a GeoServer WFS 2.0 service in a variety of the supported formats.

The service has multiple FeatureTypes which should be available for export in a single query (along with BBOX and attribute filtering).

For simplicity we are using a get request at this stage (more due to applications requirements).

I have a query like this:

http://www.myurl.com/wfs?
service=WFS&
request=GetFeature&
version=2.0.0&
count=9999999999&
typeName=a_prefix_here:feature_type_one,a_prefix_here:feature_type_two&
outputFormat=csv&

The problem is: the data from feature_type_two is not included in the exported CSV file (only exports the first feature)?

Confusingly though; feature_type_two's data is included when exporting to other formats, e.g. JSON, KML, XML?

Has anybody else had this issue?