It is its own thing, and there’s no ST support. There is some work on using a rooted Wink hub to connect them to ST. [BETA RELEASE] Lutron support in SmartThings using custom Wink Hub software - looking for testers / the adventurous
They are great little switches. I have a bunch of them. I used to use Staples Connect, which supports them very well. I set up my Staples Connect as a secondary Z-wave controller to my ST, and also set up my Hue lights on Staples Connect. I can use my Pico remotes that way to control Z-wave and Hue lights at the same time. I’d still prefer if they worked directly with ST, though.
On my long list of ST projects is to reverse engineer the Lutron protocol, and build an Arduino device to integrate them into ST. Gonna be a while.