I personally, think it comes down to how Article 7, clause 'd' has been interpreted. It's too open to interpretation and places no restriction on players who are younger than 18 when they obtain citizenship. What it says is that if a player obtains citizenship after turning 18, he has to live on the territory for five years to become eligible for the national team.
And as has been pointed out, this really doesn't seem fair to guys like Wynne. As has also been pointed out, you can apply for exemptions to this rule though (Zalalem being a recent example).