The ears...

[the phantom]

Why not consider lobes as candidates for pointing, than?

Because if the lobes were pointed Tolkien would've said so.

The quote so oft given does not even say if auricles were pointed

It doesn't have to say it. Everyone just assumes that it's the auricles that are pointed.

Here's an example...

"Vampires have pointy teeth."

Now, notice I didn't actually say that the points on the teeth were on the biting side of the teeth. Technically, the teeth might have spikes on their inner surfaces sticking in towards the vampire's throat and the biting surface could be flat.

Yet no one assumed such a thing when they read "Vampires have pointy teeth." Everyone assumed that it was the biting area that was pointy. Why? Because it's just generally known what is meant by pointy teeth. If the teeth are pointed in some way other than the usual way then I, as the author of the statement, would need to say something to specify. If I don't specify, then the teeth are pointed in the way everyone assumes they are.

Same thing with pointy ears. When people read that quote, I'd venture to say that every single person thought of pointy auricles, therefore Tolkien does not have to specify. If he had intended points on the lobes, he would've said so since no one assumes pointy lobes when they hear "pointy ears".