It may or may not be, but my testing seems to show it exhibits precision loss as well.

I've done some rather avant-garde testing with repeating command blocks putting air below passive mobs to drop them into the void and flown around with far lands off and mob spawning precision loss fixed. It seems as though naturally generated animals spawn on the very corners of blocks, but I've seen this at both 30 million and 5000 blocks out, and some placing of campfires has shown the particles to not always be generated at the same points the mobs spawn at, so I'm going to go ahead, assume that passive mobs aren't affected by precision loss and close this issue.

I've turned on the mob spawning fix and can see no precision loss. I haven't tested anything to do with passive mob spawning on world generation though.