The whole thing is time stamped. Check out the Approach to the Tower. He gets pummeled a lot by those turrets constantly clicking back and forth and wrestling with the mechanics. Yes, it's user error, but it's user error because he's getting pummeled by turrets because he's wrestling with the mechanics. And this isn't him at the beginning of the game. He's obviously played it enough that he's already at the Underdark. This is Part 36 of his walkthrough for Patch 6. He's not a new player, but he's still wrestling with the mechanics, and at one point he even makes a few comments about how frustrated he is with the mechanics.
But the biggest one is Alternate Entrance to the Tower. Yes, there is naturally user error. He could unchain everyone and move them one person at a time as they jump down from the mushroom. But the point is that it's an EXAMPLE of the bad movement mechanics. This kind of stuff happens everywhere especially in the Underdark. Jump too close to one of your own and you not only take fall damage because you jumped down from a big distance, but you also jump too close to one of your own and knock them prone and injure them. Why? Because they ran into the space you were jumping into. Lae'zel jumps back up because she's still chained to the main. You have to - one person at a time - have every single person make the jump including your spawned minions like the quasit. It's slow and clunky and painful.
Then, jump ahead to like 26:00 and you see that he is trying to cast Light, but he can't because Lae'zel is carrying Sussur Flowers and is too close. He moves Shadowheart away from everyone, and Lae'zel just pops right over to stand next to her. He has to first unchain Lae'zel, have her run to another area of the room, and then he can finally cast Light with Shadowheart.
Complex mechanics. What would be easier? I click on Lae'zel. I move Lae'zel away. Because I selected her, she was instantly unchained. I click on a button. Everyone is chained again. When jumping down. I have everyone grouped. The person I'm controlling makes the jump, and everyone follows because they are chained together. If they all get hurt, they all get hurt. That's on me because I made the jump with everyone grouped. If I wanted only one person to jump and scout the area and try to provide a safe way for everyone else to follow, I'd click on that one person's portrait, which immediately makes them no longer chained, and make the jump separately. THAT is easier mechanics. Not this make each and every person jump one at a time business, and if you forget to unchain they might actually jump right back up and have to make the jump all over again business.
THAT is the point we're trying to make here. It's clunky and slow and painful, and it could be so much easier. SO much easier.
