Personally I believe the majority of the players do not have correct sizes for their characters they make since the game worlds and their objects aren't really fitting or giving a proper feel of there being a "right" size. Just look at things like trees, paths and walkways, plants even.
In some maps they're huge, and in others they do not even exists, the run animation and speeds also favour the biggest characters, because if you make anything smaller they appear to be sliding quickly over the ground. There's many different factors why over all users have a various different idea of what a proper size for their character is but also why they'd end up using a bigger character. With this said, I cannot blame anyone for having big characters.
Over all the chart provided makes sense, and I believe most people that would just plain out see this chart would also agree with it, but how their characters would look in the game probably wouldn't. If the things mentioned above would change for the differ I think we'd see a more reasonable general size for most characters. I think the majority of the "adult" characters no matter what type of feral they are, end up on the right side of the chart, while cubs or pups end up on the far left side.
I do believe things has gotten slightly better in the game over time, but it's still very common to see wolves, warriorcats, lions, dragons, all sharing the same size in the character creator. Which is a bit amusing if they'd all be in the same area at some point.