ATC Watcher
Not doubting what you say, and not wishing to teach granny how to suck eggs, but there are two different major controls on most radars of the B747-400 era.
The first is the 'gain' or the sensitivity of the radar to the returns received - for this to be in auto is quite usual and not to be criticised,
The second is the 'tilt' of the beam, which is under manual ie pilot control, and where on the B744's I flew, auto was not available. The tilt selected references where the beam is looking relative to the horizon and will vary in various flight phases, the beam itself being about 3-4 degrees wide. At TO, for example +10degrees might be appropriate, reducing to +2 to 5 degrees during the climb phase. In cruise flight, you obviously want to know what is at/around your level and so will point it lower than in the climb. At all stages thoough, you should vary the tilt up and down to build a better picture of the overall atmosphere. I believe that more recent developments provide automated 3D mapping for the crew.
So, whilst I agree that hail may well not provide a return in itself, then the hail is coming from some cloud structure that will, and that by using the tilt you should be able to 'see' formations worth avoiding.