To be clear, closed loop communications doesn't change how evenly or uniformly an individual battery pack in a set charges. That is still done the same way. IE, if you put 57v on the bus bar, that means each individual battery pack has the *potential* to reach 57v. but doesn't necessarily mean they'll all be exactly even.
What the closed loop communication generally does is tells the charging equipment that "this stack of batteries can handle up to 100amps of charging right now." and then as packs fill up "This stack of batteries can handle 30amps fo charging right now". As a result, the equipment that handles the charging will ramp up/down the output, to keep from overcharging the batteries or charging them too quickly.
As an example, the BMS in my stack of batteries will allow the charge controllers to do a combined total of 500a of current (my equipment can't provide 500, but thats what the batteries can *handle*, as they start getting near full.. it'll reduce it. down to eventually 15a or so, and then stop. (In my system, it's smart enough to take the "excess" and sell it back to the main panel. so even though the battery isn't able to consume the rest, I'm not losing output. If the stack can handle 50a, and my solar output is doing 100a, the inverter is smart enough to invert the extra 50a, and send it to the main panel/grid. which keeps the batteries at their "50a limit"