Elf/WMG

Miles Finch actually was an elf.
He is the antithesis to Buddy - an elf who was raised by humans but doesn't know it. This explains all of his wealth, why he is so mean, and why he was so very offended about being called an elf.

Buddy isn't really a man-child.
...Well, at least not to an elf. Elves seem to age half as quickly as humans or even slower, so Buddy might actually be just as far along mentally and emotionally as actual elves his age. Unfortunately, at some point, Buddy got too big and/or old-looking and was forced to work with much older elves, which is why they treat him like a child.