I guess what they say is true: great minds do think alike.
When I was working on Dragon Magic, one of the things I wanted to do was present animals (as in, the animal type) that had some draconic heritage in them. They needed to be nonmagical and suitable for use as familiars, mounts, etc. Basically, I sat back and thought "OK, the premise of the book is that dragons are heavily involved in the world. How does this affect not only the people and civilizations of the world, but also the ecology?" And thus the drakken were born (though credit Owen Stephens with the name).
So when it came time to figure out what drakken I wanted to create, I said, "What is a player going to get the most use out of?" Well, familiars, mounts, and animal companions came to mind immediately, so that's the direction I wanted to go in. The big reason I wanted to create these creatures is because I wanted them to be non-magical animals; these are the kinds of things that evolve in your world naturally as a result of draconic influence in the world. Mechanically speaking, in the PHB all the default familiars and animal companions are just mundane animals, so I wanted the drakken to be just as compatible with the core mechanics as the default options. Sure, other books had presented options for draconic familiars, etc. but none that I had seen were animals, and none were as easy to plug in as I wanted.
I really, really like the concept of fantastic animals, and the drakken are what I came up with for this book.