What I have never understood about those charging bars, is they still use the DJI charger. It would be like hooking up 4 water hoses to the same water "spigot" (whatever you want to call it) at once and thinking you will get 4 times the amount of water,,,you won't. The limiting factor is still what the DJI charger can produce without overheating and burning up.
You could take 4 DJI chargers and put them in a case, and they could charge 4 batteries at once,,it would really just be four individual chargers acting individually, each with its own transformer, etc.,,