Comment by skrebbel

This seems very similar to Java's oldschool single-interface callback mechanism. Originally, Java didn't have lambdas or closures or anything of the sort, so instead they'd litter the standard library with single-method interfaces with names like ActionListener, MouseListener, ListItemSelectedListener, etc. You'd make a class that implements that interface, manually adding whatever data you need in the callback (just like here), and implement the callback method itself of course.

I think that has the same benefit as this, that the callbacks are all very clearly named and therefore easy to pick out of a stack trace.

(In fact, it seems like a missed opportunity that modern Java lambdas, which are simply syntactical sugar around the same single-method interface, do not seem to use the interface name in the autogenerated class)