Actually, that just sounds like convergent evolution to me. The shards and the Source were all (at least at first) the same places geographically, with the same environmental and climate challenges, so I don't find it surprising at all that they evolved similar life forms that basically have parallel niches. The thing that came up in the live letters of 'the sundered people subconsciously yearned for certain features' adds a bit of a (semi-)intelligent design bent to it, but I still see it the same; if all fourteen versions of the planet had the same circumstances that meant that, say, cat-people were a viable evolutionary niche, it stands to reason that all fourteen of those planets would produce cat-people. Especially if, as suggested in the Live Letter, they were being semi-consciously shaped by minds that knew that 'cat people' were a thing that fits the purposes they need.
It's carcinization, only with elves.