Any of the statues that you see of the Buddha tell stories. So there's always a story with each statue. The one here in the hall, the hands are on his knees and the fingers are pointing down. Actually the fingers should be touching the ground, which indicates the time during his enlightenment where he finally told Mara to leave. He finally said to Mara, "No, I have the right to sit here, I have the right to become enlightened", and he said, "Let the earth be my witness!" and he took his fingers and touched the earth. Supposedly the earth quaked throughout all universe systems. Mara disappeared in that moment for the last time in challenging the Buddha as to whether he was going to become enlightened or not. So there's a story in that statue. The statue with him walking in the way you describe, I don't know the story. There will be a story behind it, but I don't know what it is. I know a few others, but the particular one in front of the temple I don't know.
As to "If it helps my concentration is there any reason I shouldn't also practice walking like this?" Anything you do that's odd such as grab your ear when you are walking, well, if you keep it that way, it will help your concentration. It may not help your wisdom, it may not help your compassion but it will help your concentration. So we don't advise doing it, because concentration increases but other aspects of the practice decrease. To have your hands relaxed, maybe in front of you or on the side, wherever, but not creating anything special which will draw the attention to it and keep us focused in a different way because the focus is intended to be on the walking. So we actually don't advise doing something like that but we do know that it could help your concentration yet other aspects might suffer.