*I cant believe I'm having to remind someone of their own club's processes, but ok...*
Kids who first get into Ajax's youth set up start there when they're about 7 or 8 and will have been scouted in advance and then invited. They scout within a 50km zone from Amsterdam so Klaassen should have been well mopped up. He wasn't. He was transferred twice before reaching Ajax at 11 and would have been seen as one they missed out on and had to get in. Coaching is fluid at the club and coaching at different age groups isn't seen as more important with one group than with others. The coaches of each age group are all ex-club players and it's inconceivable that the head coach wouldn't hear about a player with talent that'd been brought in at that age. To believe that a head coach at Ajax would only become aware of talented youngsters when they burst into the older academy teams just beggars belief.
Koeman himself was bemoaning the fact that Ajax dont start their scouting as Feyenoord do at age 6, so it's a long shot that he, whilst at Ajax, wasn't looking closely at what was coming through the door at a much later age than that.
What is the relevance in this?
That he didnt join AJAX at 6 but instead, 11?