Found this when looking for calls to addModuleScripts(). In Flow:/includes/Content/BoardContent.php#L200-L224:

	$parserOutput->setText( $childContext->getOutput()->getHTML() );
	$parserOutput->addModules( $childContext->getOutput()->getModules() );
	$parserOutput->addModuleStyles( $childContext->getOutput()->getModuleStyles() );
	$parserOutput->addModuleScripts( $childContext->getOutput()->getModuleScripts() );

This should probably use addOutputPageMetadata() to avoid hardcoding calls like this. It's code duplication that's likely to rot, go out of data and cause weird and unpredictable corruption. For example, it seems it already forgets about getJsConfigVars() which means it will miss certain variables causing extension tags for Maps to probably be broken.

See T140920: <mapframe> is not visible in Flow (blank frame).