As I said, it would be faster, not exactly simultaneous. Feel free to suggest a more accurate name for the fire mode. For example, if a rolling broadside completes in 3 seconds, simultaneous mode could perhaps complete in 1.5 seconds. And of course, it doesn't have to be exactly twice as fast - the particulars and what it is called isn't important at this point. The suggestion is to make random fire mode faster so it's useful.
It's not, I am quite certain, as I spent time testing exactly that. My Bucentaure, for example, completes a rolling broadside in 5.5 seconds, and a random broadside in the same amount of time.