I agree with the principle up to a point, and the numbers provide some perspective. Also 12p in 16 games is not exactly bad or even mediocre for a young first timer, unless your name happens to be Laine, in which case I think it's fair to expect just a bit more (though not much...). I don't really agree with the thinking hitting the post is bad luck. It's still missing the net, it's just missing it by a very tiny amount

The way Laine picks corners he's bound to miss the net and hit posts a bit more than many other players, I think it's just his shooting hasn't been at its best and the margin for him is very small - he scores a lot of his goals from areas and chances where he has to get it right on the mark. He regularly scores goals which would basically be flukes for most other players.
His high shot number seems to be partly from just shooting more than during the regular season. This seems by design and some of those shots have led to assists from juicy rebounds or bounces. But at least to me it seems he's not as selective with his shooting as usual, so a lower percentage is to be expected, just not quite this low - he has been a bit snakebitten and 5 posts is a lot.
It's a bit funny though there's even a conversation about this when a player is having 0.7-0.8 P/GP in the playoffs playing 2nd line minutes. Usually that'd be pretty good even if you're on the 1st PP... In any case I'm not the slightest bit worried about Laine, I'm seeing the playoff mentality and will to win I'm expecting and he's already scored some big goals in key moments, it's just it seems his body perhaps can't quite keep up 100% of the time. He seems to be getting way more criticism than he deserves, if anything he's been average (for him) while there are a bunch of people in the team seriously underperforming and there doesn't seem to be much talk about those players.