Ok, so I've done a little testing to try to confirm this, and I believe the results are consistent. Bats seem to have their quality capped by the survival of the person killing it, and they appear to be the only animal that does. Am I missing something, or is this a bug?
For the record, I don't care which way this gets fixed, but it definitely feels like it needs to be fixed. Either make all animals work this way or none of them. (I lean towards "all of them" m'self)