Does Secondary Audio work w HLS?

I got this to work with some help from a friend.
Difference is using "AlternativeAudioProgram" - I was trying to use AudioLanguageSelected from the docs, https://sdkdocs.roku.com/display/sdkdoc ... Attributes

Why can't I find in the documentation any mention of "AlternativeAudioProgram" which is the metadata element that made this actually work?