Don't know which of the events you are refering to, but I think there are a couple reasons, good and bad.
Popular conseus on prospects usually takes some time to change, which can for example be seen in how long players who were very dominant/productive very early can stagnate or become relatively weaker to their peers, and still have a very high standing for a long time. Ivar wasn't dominant at TV-pucken, I don't think he played for Sweden at all in his u16 year, and didn't have as pretty of a statline as some of his peers that developed earlier. I probably was higher on him than average, mostly because I kind of assumed he would at least get closer to his brother in terms of the physical attributes, and he was definitely skilled even early on. As soon as he got more and more power in his legs he rapidly improved relative to his peers, and his confidence clearly took a jump as well.
And to be fair to a lot of people, you can't always assume those things will come. Just look at Filip Ekberg, who was way more advanced in terms of gamesense very early on, but whose physical tools have been close to completely stagnant for years now, and due to the pace and skill difference now, doesn't even look smarter anymore(or at least at the end of last season, haven't watched him in the OHL this year).
I believed Stenberg would probably end up as a more skilled version of his brother at the beginning of last year, maybe slightly less wellrounded. His constant improvement has been absolutely bananas to see, I did definitely not expect him to be this good at this point. Very good example of multiple things, the potency of skill and intensity, the importance of not locking into point production at an early age when evaluating talent, and just how much different development can be for players who gain their growth a bit later.