Well, as you point out, unprecedented is unprecedented. In which the "when" becomes a bit open ended. But I also know that judging purely by counting stats is not the way to go. The kid has an on-ice shooting percentage at a hair over two. That is so low as to be comical. But the when you look at expected goals and generation of high end scoring chances when he is on ice, the numbers sky rocket. So how do you square that? Well, not only is it poor puck luck, but his line mates being incapable of converting what Lafreniere sets them up with. Is that a reason to be worried? Not to me it's not.
Then there is the fact that by the strict eye test, Lafreiere really does not look overwhelmed or that the game is too fast for him. Is he tentative at time? Of course he is. He is a 19 year old rookie with a ton of expectations who has known nothing but counting stats. So yeah, I would say that he looks tentative at times is hardly surprising.
You keep harping on "writing the season off". That is not what is being done. The only thing being done is putting things into proper perspective. When does that change? When it looks like the game is too much for him or the analytical stats start to tell a completely different time.
At times, I find it is necessary to blow things into the absurd level to help illustrate a point. If Lafreniere did not get a single point all year, but managed to net 40 in the final game of the season, would you then say that he has had a fantastic rookie season?