Can't get that link to work, is it about the late developers program, where they run two pools of players? Belguim's that you mentioned was referenced in the FA bootroom magazine, very interesting and something I like. Granted I fully support this for personal reasons, leaving for uni in 2000 having just turn 18 I was barely 5ft9, three years later, 6ft and 1/2 inch! (hey 1/2 is important to a bloke!) so I am well aware about developing rates, also remember being told Steven Gerrard grew between when the FA measured him at 21 and 22 as part of their National team stuff.
I am sure Hazard was mentioned in the article about someone out of the late developers program for them, a player I mentioned in here for my school side that was technically superb, but small, and who made a couple of development teams and was always let go (Sheff U and Barnsley) is now about 5ft8 or 5ft9 at a rough guess, which considering he is only just 16 shows that to me he isn't too small, despite having been labelled that continually for the last 5 or 6 years, he isn't far off the having the physique of the lad he played up front with who was our "big kid", problem is now he is considered too old, I appreciate I am biased but he has stood out continually, in a variety of positions, for one of the worst school sides in Rotherham and plays in one of the higher divisions in his league and has something like 200 goals and assists in the last 5 years.
To me this is why you gets the likes of Vardy, Gray etc. Some people just develop much later or have a sudden surge of athletic ability at a certain age.