To take your point farther, I've met plenty of people who've learned their second language as an adult and can speak nearly accent free. As far as I can tell, the only difference between those with and without an accent is conscious effort.

The whole idea that there's a window that closes when you're a kid has seemed a little weird to me. Adults learn new vocab and grammar all the time. Learning another language is the same, just a little more extreme.

I wonder if there's some actual scientific evidence for the language learning window, and not just some developmental psychology observations.