Until you get a real answer from someone prominent

I can keep on guessing.
The return from such api call is an array. Maybe if you do a
print_r($modx->getTemplateVarOutput($); (or possible the getTemplateVars or getTemplateVars) it could give you a hint.
Once again, I’m just guessing, at least it keeps this tread bumbed up
EDIT: And it gave my en extra star, 100 posts already...