If you think shot selection isn't a part of hockey IQ I think we may have a different opinion on what the term means. I would think about decision making quality + speed, space mapping, timing, predicting and reading the play before it unfolds etc. way before I would ever think about hand eye coordination, but I'm certainly no expert in the subject.
I don't even know how many times this year I saw Matheson totally ignore a wide open Slafkovsky set up for a one timer to take a totally unforced point shot with no lane open that was subsequently blocked. I don't know if I would say that his IQ must be good or else he wouldn't be on the PP when I believe it says more about the quality of our team and having no other better options. He's certainly one of the better offensive dmen in the league but I would attribute it to his all-world skating and physical traits.
Active ignorance or conscious ignorance. This is why this isn't always about IQ because it's a situation where the not doing something is active and Matheson is the general having to think 1 pass ahead. And then the player receiving the first pass need to do something predictable and the play Matheson has planned. This is why a rookie like Slafkovski often gets ignored even completely opened, That will change over time as players gain trust in Slaf's finishing/passing/play reading abilities.
I agree IQ plays a role in it (plays a role in everything really), but you have to be aware that what you are judging is in a effect risk management calculations over multiple plays.
You're the first person I see labeling Celebrini as generational
He's on that line between Generational and Franchise, I think given his skating and defensive game, he will have a generational impact. For example, I can imagine a matchup Celebrini/Bedard not turning in Connor's favor at all. The thing is, most of the players in the next few drafts, and the players that will be left when Celebrini will be in his prime (McDavid/MacKnnon/Mathews out, Hughes/Hagens/Bedard/McKenna/Jacobson in) all have a smaller bodies. In his cohort Celebrini will be a fast skating giant.