The idle speed screw certainly should do something.. it actually opens the throttle slightly and is no different than turning the throttle grip..
Look close at what happens when that screw is turned.. it may not be the idle speed screw at all. Adjust idle speed (and, if available, the idle air:fuel mixture, ) only on a hot engine. Otherwise the hot engine won't idle when you come to a stop sign.
And i like the idea of a manufacturer who values comfortable testes..