I have three (3) GE Smart Dimmers wired in a bank BEHIND a three way GE Smart Switch, all of which are working perfectly. Under this configuration all of the dimmers are powered off/on with the three way switch; in other words, the dimmers are completely powerless when the switch is off. I was curious as to what state the dimmers would return to once they were powered on with the switch. As it turns out, once the devices have a history of “recent” activity, they return to the last know state; in other words they operate exactly as the legacy switches they replaced. This is contrary to what the support techs will tell you.
As a side note, these dimmers will create an exception flag in the SmartThings app. This can be cleared by tapping on the device with the flag, closing the message window by tapping the “X”, and then refreshing the device by tapping on the circular arrow.