The tools aren't going to change much from a scout seeing someone 5-10 times or them playing 40 games against better competition. Your arm is your arm regardless of who you are playing. Your speed is your speed. Your range is your range. Your bat speed is your bat speed. Your instincts and hands in the field are the same.
Everything crystallizes against better competition. Why do you think showcase events are scouting meccas? When you "project" a player, much of what you're trying to do is guess how he will play against better competition. The game speeds up, and the questions become, can the tools "play up" and does the player have the instincts to handle the faster game...
Big step from high school ball to pro ball. Plenty of guys start slow (like Jeter and Chipper Jones), so too much importance should not be placed on a high schooler like Hamilton struggling. On the flip side, though, when a high schooler plays very well, like Silva did, it should make a strong impression, IMO.