I consider abstraction to be about giving various concrete things the same representation. In this case I'm saying that we're over-abstracting by pulling too much of the dissimilar code between the examples into the one representation (i.e. the method). I would also say with the `average` methods it's not quite the same operation, despite having the same name. The over-abstracted method had quite a bit more going on internally than the minimal abstraction, and had a different interface.

With your dog walking example, I'd say each of your listed abstractions would be 'the right abstraction' because you're not bundling up dissimilar things into a single representation as if they were similar. Specifically with dogs/humans, my example about circles/squares is the same: both might conform to the same interface, but you wouldn't want to represent them with the same class. I agree that doing so is perhaps a special kind of mistake for which there may be a better term than 'over-abstraction', though it's not obvious to me what that term would be (over-specified doesn't quite sound right to me).