General Andrew Jackson's statue is an example of one that doesn't follow the code. This is because the horse has two hooves raised implying that he was injured in battle but in reality he died a peaceful death, and was not injured.
Although many statues confirm the code, others don't. So we have to draw the conclusion that there is no specific code, being as there is no specific pattern.
I think it's really cool that sculptors had, and have such a creative and artistic eye, that they can address and identify through their masterpieces. The result of an event that the rider in the statue confronted.
I found it fun and interesting to research this claim and see how we can identify patterns, like this, with our brains.