Sorry but I think they knew how a development process works even before going to 2019 E3 to release interviews to the press.
Underestimating development process or how much content will be implimented is a common mistake made by game devs. And if you watched recent BG3 live stream you would see an example of how the game constantly gets bigger as devs finds new cool interactions which were no planned before.
If at a precise question "will Italian language be supported"? You reply "absolutely yes", you make me think that you know what you're talking about, so it's hard to believe they underestimated this task. Consider, please, that we're talking about a major feature (as I also pointed out previously, in a part which you didn't quote). In any case, for me, what they had and are having is not acceptable behavior.
We must not promise what we ought not, lest we be called on to perform what we cannot. Abraham Lincoln, 1856.
