EV battery engineer here. It's not hard. Battery management systems are often over engineered but the state of the art is fairly straightforward and will allow battery packs of sufficient size last 200k miles or more easily.
I dunno the PhD electrochemist that I know who spent a long time teasing out the conditions and requirements for megapack operation didn't think it was trivial. That's also the reason Tesla pays Jeff Dahn so much money. A million miles/20k cycles is the goal.
The electrochemical interface where lithium intercolates into the anode and cathode of the battery experiences microscopic electric field variations that, depending on the local surface geometry, lead to side reactions and battery degradation. The hardware that converts DC to DC and DC to AC must be designed to mitigate the voltage ripple and harmonics that exacerbate the localized electric field extremes that prematurely degrade electrode interfaces and battery electrolytes. State of the art BMS and rectifier components are much more difficult to build than you might think.
Correct me if I'm wrong but your comments do not suggest that the end result of this engineering cannot be very simple, elegant, and hopefully even inexpensive if built at scale. Instead, they suggest that the team who builds it needs to know what the heck they're doing.
Why should it lack that? That's a tiny piece of software in the charge controller, which on this vehicle ought to be some tiny microcontroller.