How is RW 7.3 release Note "Added support for theme updates" supposed to work?

It reads: Added support for theme updates, developers will first need to update their themes to take advantage of this.

What does that mean to users?
How is theme updating supposed to work?

Thank you

The developers will have to update their themes giving RapidWeaver the ability to update them. So this update will need to be gotten by the developer first. Once they have done this and you have downloaded the update. Then it will update like Plugins, tell you when you start that there is an update and give you an option to download it or skip it.

It is unclear if the theme update feature is (1) functioning and (2) supported yet by developers. Are their any themes that support this feature ?

As far as I understood it it works the same way the Waterfall-Plugin already does, so basically Waterfall-enabled themes could be updated with this built-in theme-updaterโ€ฆ