I'm aware the "uniques" metric has been deprecated in the Youtube analytics API. However, the new youtube studio beta shows some sort of derived "unique viewers" metric, as per https://support.google.com/youtube/answer/7577916?hl=en Indeed, I can see this metric by clicking on "Analytics", then "Reach Viewers" via the Youtube Studio Beta web interface.
It seems there should be a way to grab this metric via the Youtube analytics API, and yet I can find no documentation on how to do this. Is this possible, and if so, how?