You are welcome; but, in fact, I was not actually correct! The change to sequenced actions took place when 3e was released; each actor ( in initiative order ) completed their 6 seconds of actions before the next actor decides what to do, and the DM lost their choreograph role at that point. What 5e added was an explicit categorisation of actions/bonus actions/reactions etc.
This means that the NWN games were using 3e stats, but still operating under 2e concepts of simultaneous choreographed action - a hybrid of sorts. My initial incorrect assumption about 3e ( which I just checked and found to be wrong ) came about because I did not play TT after 2e, but did play the NWN games, not realising they did not represent the new TT rules accurately.
Which still tracks for me. I enjoy BG1&2 a whole lot, but not so much NWN2, Kingmaker gameplay wise - I find there is too much to control and micromanage to make it transparent and enjoyable. An odd one is Icewind Dale2, which was based on 3e I think and I remember enjoying it a lot, but I don't remember it being as detailed with various modals or attacks of opportunity that are found in later games.