I will agree that for all Larian is within their rights to stop working on the game, and for all they can announce that how they like and I will even say it's probably good that they announced it relatively early, Swen saying that they're elated to not be working on DLC is kind of in poor taste. Breaking the news slowly over weeks isn't the answer I don't think, but they still could easily have done better. Not releasing a formal announcement on their platforms for example, feels like a misstep.
That being said, I do think the focus on this aspect of the OP post is missing out on the larger point being made in it. And I think those points are way harder to dispute. I'm certianly not going to be buying anymore Larian games period. Their style just really is not for me, and as a studio from what I've seen from people talking about them on the forums, etc, they just have a bunch of glaring issues that they don't seem inclined to fix anyway. They do just seem very immature as designers, with little self-discipline in terms of executing on ideas and knowing when to pull back or not.