But with no clear user-facing way to activate it, meaning you have to use some unofficial app that accesses it in an undocumented manner, it has the smell of something that you could not rely upon as a "feature."

If it's there and it works, then great for you, but you can't expect a whole lot more. It sucks that they didn't actually make it a published feature with an actual means of accessing it, and take on the responsibility of maintaining it, because it seems like something I'd like to use.