I still say that it's too subjective to make broad blanket claims about, because everyone's situation is different, and that's where I disagree with you.
Again, take my situation. Where I grew up, I never felt like I was a part of it or that it was a part of me, despite living there for 18 years. However, in my current city that I have only lived in for 4 years, I do feel that way. I feel more at home and at ease here, and more in line with the culture than I did in the country.
I know people that have lived in this city their whole lives yet never actually experienced half of the home-grown culture, whereas I do everything I can to seek it out and experience and be a part of it. Hell, I know people that haven't been to local resturants that are defining features of the city despite living here longer than I have. I would argue that I can call myself an Akronite more than they can, despite their nativeness, because they aren't, well, a part of it.
Making broad claims like you're doing completely negate situations like that. There are certainly people that choose to identify with a city when they shouldn't. But saying you have to grow up somewhere to identify with a city is just a really, really bold statement that ignores a lot.
I agree that it takes more than a year to call yourself a member of a city, as it took me almost 3 years to even feel comfortable saying that. But there's a huge difference between doing that and doing what Sarah did that you're so critical of, or at least from what it seemed from what she wrote.
"I'll die before I surrender, Tim".