The argument is that it's a difference that adds very little to them. Subjective, one might say, but if you're presenting it as a selling point, it falls flat for me.

On 2, yes, if you mean to compare them to rabbits or hares, their evolutionary history is distinctive and unique to them. Just by virtue of having rabbit ears creates no further obligation to introduce the myriad of other rabbit traits out there, much like miqo'te don't have claws or whiskers simply because they're related tangentially to cats. The point being that having rabbit ears commits SE to nothing further than that.

Finally, I can "understand" why someone might be excited for it, but I don't care to see the max height options for males curtailed for that reason. Want them to be the same? Fine, whatever. But I do not want to see their height capped just to be "different" in a way I scarcely care about.