Why do all polydactyl breeds have similar standards for toe placement/spacing?

[Cloverr39]

I recently read the standards of a couple different breeds with the polydactyl gene (extra toes) and it seems all had very similar if not the same descriptions for what the toe placement/spacing should look like (unless the information I read was incorrect). All said that the 4th toe should be pointing down and the 5th should be pointing up. Is there a health or quality of life reason all these breeds have a similar standard for 5 toes or it a coincidence?

 

[Ponyiqandhens2]

There are several reasons although kinda strange..there are two types..the extra toe comes from the same mutation for all but the Houdans which the extra toe comes in differently. Anyway, it is a dominant trait and been narrowed to a specific gene. I can understand the 4 being the same based on what I learned