The problem that guys like Tercet have (and he's certainly not alone, this applies to anyone who seems so absolutely certain about anything) is that for every prospect and player, there is a range of outcomes that they refuse to account for. So take Teoscar, maybe entering the season he had a 5% chance of becoming an All-Star, a 30% chance of becoming a regular, a 40% chance of becoming a 4th OF, and then a 25% chance of flaming out and being minor league fodder.
Perhaps someone like me would give him an increased chance of becoming a regular and a decreased chance of flaming out, but I'd definitely consider all ranges.
But someone like Tercet probably would give him well over a 50% chance of flaming out. To further compound the problem they consider anything over a 50% chance of happening more in terms of a 90-10 split when it's really closer to 50-50 or 60-40. Nate Silver has discussed this phenomenon before. Not sure if this makes sense but I'll see if I can find Silver explaining it.