It's really not that surprising when your job is
Takes a)your team actually listening to your input over others b) using that input and making the final decision off of it, c) waiting five plus years to see if your decision/input was the right one, D) determining whether outside influences (development, injury, etc) influenced the outcome of the decision or if the decision was wrong in the first place.
Add in the fact that many GMs aren't with a team for the five plus years necessary to actually validate any of their scouts work, all of the validation comes from internal scouting directors, who in turn have very rarely actually been validated by anyone, and it's gets muddy really quick.
Finally, when you think about it, we're changing the fundamental view of what's effective/good hockey right now. The new viewpoints have not had time to trickle all the way down through every hockey function and so scouts are still likely to mis-prioritize certain attributes.
Players like Stanley represent a market ineffeciency exactly BECAUSE many scouts rank them high, when their probabilities of success are actually quite low.