Hm. I think the refresh command is making the core re-requesting all channel values.
openHAB does only support commands on channels not on Things. And that’s what is required for the mentioned actions.
Regarding MQTT. The thing is that the underlying library (paho mqtt) is full of bugs and only maintained by one guy that only occasionally works on it and currently focuses on mqtt5. And its an eclipse project 
paho would need to be replaced by that other mqtt library (forgotten the name but linked in one of the issues). That’s unfortunately a Core contribution, which I’m clearly not doing at the moment.
paho has several subscription bugs with the async API that I’m using. Most of the java people out there seem to use the synchronous API which apparently works (most of the time). I don’t see a point in working around in the mqtt binding when the actual bugs are further down in the stack.
Cheers, David