Is "you know you know" necessarily a redundancy?

From the “Ithaca” chapter of Ulysses:

What, reduced to their simplest reciprocal form, were Bloom’s thoughts about Stephen’s thoughts about Bloom and Bloom’s thoughts about Stephen’s thoughts about Bloom’s thoughts about Stephen?

He thought that he thought that he was a jew whereas he knew that he knew that he knew that he was not.

OP, how about this one?

Yeah, possibly also “I suspect you might claim you don’t know, unless I assert ‘you know’ in this way”

How about mystery novels?

Like, you’ll see an Agatha Christie type set the stage by throwing out a bunch of details — maybe two women are set to inherit everything following their father’s death, and they’ll mention that his will actually leaves a ton of it to their long-lost and presumed-dead brother Larry. And they’ll add that Larry was left-handed, like Grandma, and a redhead, like Grandpa, and colorblind, like Dad, and prone to drinking, like Mom, and was always making a big show of writing down stuff in that diary he always then hid somewhere.

And then, on the day the will is read, a red-haired guy shows up and gloats that, as he’s Larry, he’s entitled to all those paintings on the walls. And he leads them straight to where the diary has been hidden all this time, and he left-handedly unlocks it with the tarnished key he’s got with him. And in maybe Chapter Nine we get a bit where he offers the amateur sleuth a drink, and gets asked to our it inthe green cup instead of the red one, and complies.

So he’s not the long-lost brother; the reader now knows the brother is colorblind, and knows this guy isn’t colorblind. But: does the reader know that the reader knows?

I have visions of you doing this.

mmm

While sleeping in a hole in the road?

To me “you know you know” (generally speaking) implies confirmation of a suspicion, as opposed to simply an acknowledgement of fact.