SourceMods & TRIANGLE_STRIP primitive?

I have a Custom geom::Source class which I’m trying to duplicate using SourceMods, as described here;

Something like this:

geom::SourceMods combined;
vec3 offset(0,0,-1.0f);
for (int x = 0; x < 10; x++) {
  combined &= CustomSource() >> geom::Translate(offset * vec3(i));

This seems to work fine with the default geometry sources, but my custom geom Source class uses the TRIANGLE_STRIP primitive, which doesn’t seem to work (I tried a lot of variations, but basically when I changed my custom source’s primitive to TRIANGLES it finally worked).

Is the TRIANGLE_STRIP primitive simply not supported for SourceMods or am I missing something?