If I understand the question correctly it is, what difference does it make to simply call for notification of the victims in circumstances of a joint submission on sentence? What does that add? The answer I would give is, a joint submission on sentence is something that you know before you arrive at the court. It affords an easier opportunity to notify the accused, because it isn't a deal that's made on the courthouse steps.
A joint submission is almost always the result of prior negotiations, and something that you know when you get there. Therefore, the circumstance that I described where a deal is made on the courthouse steps, and then the whole thing has to be ground to a halt with the attendant delays and the attendant injustice on victims, is less likely to occur where the arrangement between the crown and the defence has resulted in them agreeing on the sentencing proposal. It's asking for half the loaf, quite frankly.