I believe that Larian has some emotional attachment to this system. It looks like something you created and deeply believe is good, but everyone says it isn't. And although it isn't a terrible solution, the chain/unchain system is no better than the classic mode (BG1, BG2, Pillars of Eternity, Pathfinder Kingmaker...).
So, Larian needs to give this up and implement a better system (the classic) in which you simply click on someone you want to control or draw a square on the screen to select more than one character. Or select one of them, hold Shift and select the others (Backspace to select the entire group).
Perhaps they can adopt a mix of these two systems where if you select more than one character, it will show a lock for you to "link" the characters together.
And the game really needs Formation Options because it's frustrating to see your group taking strange positions on the battlefield before each fight.
Agreed, though personally I find the current party control system terrible, in every sense. Has there been any acknowledgement by Larian of the feedback on party movement? Surely they can't stick with this system? They seemed to act fairly quickly on the feedback about the companions but I am not aware of any comment on this feedback.
I would hate to think that that their pride or insistence on their vision for BG3 would get in the way of implementing a superior party movement system, even if the basics were devised in a previous game over 20 years ago. As they say, if it ain't broke don't fix it.