Sure they are a risk, but if scouts saw him as having first overall talent, they would go higher then the second round IMO. 2 inches and 20 lbs isn't that much of a difference. Samsonov is still tiny, and size was seen as more of a factor when he was drafted.
2 inches and 20 lbs is a big difference when you're only 5'6 and 160+ lbs.
None of those guys came even close to Samsonov at the beginning of his career. He was in the IHL at 17, won the Calder at 18, and scored 75 points at 21. None of the others were NHl regulars at the same age.
Gionta, and St.Louis weren't even playing in legitimately scouted leagues, in their draft years.
Cammalleri went in the second round as well as Grimaldi so there isn't a lot of difference there. One think I can tell you is that Cammalleri doesn't have first overall pick talent. Should have been picked higher, sure, but not first overall.
That's not the point. Just because one small guy went high doesn't discredit every other small player that's hyped but doesn't go as high. And as you point out, Samsonov played in a much better league heading into his draft. That helps alleviate the scouts concerns about his size. Most, if not all, of the other highly talented small guys didn't have that opportunity to help shed some of that worry prior to their draft. Scouts are wrong a lot. That's the point. Just because they were right on Samsonov to take him that high doesn't mean they weren't wrong on Gionta, St. Louis, Cammalleri, or possibly Grimaldi. On the flip side, it doesn't mean Grimaldi would have actually went that high were he 5'10 or that he'll turn out as well as those guys either. It's impossible to know. But if you want to split hairs on perspective, by all means, but it's not as if people are pulling this out of thin air. There's plenty of chatter from scouts, legitimate sources, and NHL teams that have stated as much as well.
Oh, and NCAA hockey isn't legitimately scouted? That's news to everyone.
And Kane completely outshone the better talent he played with. That helps Kane's case, not hurts it.
Grimaldi is clearly a good player, but I think that his talent gets a little exaggerated because of his size. Everyone like a good underdog story.
You can twist stats however you want but comparing player's production in a far superior league to another player's production on a weaker NTDP team in a much better league isn't apple for apples. Phil Kessel outscored Pat Kane. Does that automatically make him better too?
Or I could flip it and say Kane didn't get promoted to the U-18 team as a 16 year old like Grimaldi did either. As I said, we can twist the stats however we want but comparing NAHL stats to USHL stats is absurd.
On your last point, it's possible. Or you could see him play multiple times to see what everyone else has seen. Maybe you'll agree. Or maybe you still won't. But it's unfair to act like Grimaldi is and was only getting hyped because he's a small, albeit talented guy, and people thus like the underdog story. There's a lot of tiny players that are extremely talented at the junior level that never get the hype Grimaldi did and that's for a reason. Don't believe me? Just see what John Gaudreau did this year in the USHL and the corresponding pub he got.