Sure, some people in that academy were not very good at evaluating talent, and you surely do not see the contradiction between "... can't even begin to assess ability until ... 17yrs for boys ... Gareth Bale's story is a good one (confirming that)" and the facts that he debuted with Southampton at 16 (before you continue with the argument let that sink for a little bit, he debuted with a major professional team at 16!) and played for his U17 national team. Maybe Bale just walked from his rugby practice into a professional soccer locker room and they made him play just for fun?
The careers of young great players in these top academies can end rather fast for many reasons, but I have never heard that one's ended because an athletic 18 year old good at basketball or ball dancing came to take his spot. That is the main point of the message. I had a good friend and neighbor that at 17 was a top player in my country, was the star in a final where they beat the base of the eventually absolute national team (which included the guy generally considered the best coach in the world these days), and retired at 21 without making it to first or second division. I think he was somewhat depressed for a few years. Situations like this one are the norm, very few get to the top. Moral of the story: always have a plan B (at this point and in the case of girls, College is plans A and B) .
But everybody who makes it to the top was a very talented player at 13-15, and without a lot of training since much earlier almost nobody can get to the required skill level by the time you are 13-15. This level of commitment was not needed for the US women soccer program until recently, and players could start much later, do something else, play HS or watch TV, because there were no real soccer countries that cared at all about the women's game. This has changed now (7 European countries among the final 8 in the last world cup, is further proof needed?), and the formative years of our girls adjust to the new reality, or within one generation the US women soccer team will be as irrelevant as the men team has been for ever.