As an avast user I have no power over default actions, but I would expect it to have very similar action of the file system shield (FSS) and that has multiple options on actions to take depending on the detection type (Virus/PUP/Suspicious).
So it is somewhat different to the deepscreen function, which may be called by the FSS and the file wouldn't be scanned unless it was an unknown file. In order to say if 'it is an unknown file,' I guess that it would have to refer to the avast cloud database.