I’m afraid I can’t really help much with this. To me it seems the API is still evolving, i.e. not considered stable enough to be allowed in Harbour. But I don’t really have enough knowledge about this API and what kind of plans exist for it.
May I suggest you add a question about it to the agenda of the Community meeting on IRC 29th Oct 2020, so that we can get an answer from the sailors who know more about the topic?