All my own definitions, of course. I'm not trying to convince you or argue, just clarifying my own perspective.
Of course, that's how I see it, and why I said I hadn't found an official definition of it (dictionaries don't agree on every word anyway). It's interesting to see we understand it so differently.
I misunderstood what you meant with De'Arnise Hold and Windspear Hills. But I'm pretty sure there are mentions of the world outside VVardenfell in Morrowind too, that you can't access - I'm not going back to the Vivec library to get quotes though!
It's nice to have a setting that is larger than the world you get to explore.
So in this thread, I'm addressing the arguments in the article, so I'm using the features mentioned (and criticized) by Angelo M. D'Argenio.
In
his "open-world games", there are empty ("uninteresting") areas the players must travel through, between a few areas of interest in which they do the quests they want and skip others, whereas in his "linear games", they are transported from interesting place to interesting place, no waste in-between, "linear" progression of quests (*).
And so, in my perspective, Baldur's Gate falls into the author's open-world category, because there are uninteresting (**) parts of the world you have to travel through, and a significant degree of freedom in how you tackle the quests.
(*) actually, I think "linear" is not the correct word. I prefer the notion of quest "gates" whose lifetime are much narrower in those games in comparison to open-world games, in which quest gates which remain open as long as they make sense.
(**) "uninteresting" means "empty" in this context, IMHO it's nice to explore, that's also what is expressed in the link I gave earlier (
https://www.reddit.com/r/baldursgate/comments/cin8m6/bg1_is_a_lesson_in_designing_open_world/).