After a considerable amount of usage, I am prepared to declare that the FW 3.0 animal eye-AF is not quite ready for prime time. It does not work reliably with any lens in any situation where the animal is not stationary.
Thanks for sharing that. I also watched Jared Polin's (aka "Fro") recent YouTube piece which arrives at the same conclusions. He is surprisingly objective and much less obnoxious than usual. Although it took an hour of my time to watch, it was worth it, as it will save me countless hours of frustration attempting to modify my technique to make this feature work.