The TL;DR argument against philosophical zombies is more like: if consciousness is non-causal (the consequence if p-zombies can exist), then the answer to the question "Why do I think I'm conscious" can not in any way make reference of the fact that you actually are conscious. Suppose we take the two parallel universes, and we run the same experiment in each, where the conscious and non-conscious doppelgangers are both asked the question "are you a conscious, self-aware human being?" Both of them will answer "yes" of course, and we can record and observe whatever we want about their brain states on so on, and get exactly the same results for both.

So, only one of the versions is correct, but it's only by coincidence! All the reasons that the conscious brain has to think it's a conscious human being, and answer "yes" to the question, are also in play in the zombie universe, which also answers "yes". The only difference is that in the "real" world the non-zombie brain happens to be right, for literally no reason at all.

And I think it's around this point you're supposed to realize the absurdity of the thought experiment.