Not sure I agree with this.
I have no idea whether this is indeed the continental system or not but I would have thought that a player getting into a youth system at, say age 8 and then being guaranteed his place until he is 20 would be a bit of a disincentive. A year by year system would seem to me to actually have quite a lot of incentive about it.
In addition, keeping a whole host of players on until aged 20, regardless of whether a club has changed their mind about them or not, would possibly deprive spaces to later developers.
IMO, one of the great problems with football in Scotland is that so many youngsters have no work ethic, don't look after their bodies and succumb to drink and drugs.
A country such as Holland also has the advantage of a large immigrant population where the boys are physically bigger and stronger AND have a desire to work hard.