Not sure when they started the metrics, but the initial ones were in place in 2006. Demo'ed at the draft preview night in 2006. My understanding is that has been enhanced by FJ each year and then significantly enhanced with BH coming on board. The club has been quoted that all AFL players get graded this (ours and opposition) as well as all potential draftees. It was a key in chasing Houli and Grigg apparently.
The Collingwood age of development was also quoted in the HS. But you're right it was on here too.