If I wanted the crew to report visual I would ask if they were visual. If they didnt call visual and I did not need it for sequencing then the aircraft would be processed for the IAL appropriate.
Controllers using surveillance based control (cant call it radar cause it is all digitally manipulated these days!) will assign the lowest available level on radar terrain appropriate for the flight segment being flown. If the level is not based on the RTC then it is the CTA steps or appended by the word visual once you have called visual.
Anything else is superfluous as AIP is reasonably clear (oxymoron I know) about what levels are assigned. However, if you are in doubt as to the level being assigned - ask, controllers are not fool proof (yet).