And you missed the point. These are not just any brown birches, but brown birches that grow straight, and tall, and with a single trunk.
In brief, they are different than other brown birches - a lot different!
Are the birches the same species? This is the kind of thing that DNA testing might be able to resolve. I don't deny the possibility that Chinese may have reached the Americas before Columbus, but I'd like to see some more definite evidence. Why would they come to Indiana? The Ming emperors were not especially fond of basketball, were they?