Don't see how you can keep things moving along and have 'flow' with TB combat, but more power to Larian for thinking that they can! And as someone who hates TB combat precisely because of how ridiculously, tediously slow and clunky it is, I'd be very happy if they somehow manage to come up with such a miracle.
Have you ever played pen and paper, or better yet, DM’d? Maintaining flow is a huge part of keeping turn based games engaging.
In a video game, a lot of this has to do with presentation. You want actions to feel quick and snappy in order to keep combat from dragging too much and feeling clunky. But design also plays a part. As said in this interview, if every enemy action was interrupted with a prompt to the player asking if and what reaction they wanted to use, this would feel disjointed and break the pacing and flow of the turn based system.
