The honest usage of “it turns out” is usually to gloss over an unnecessarily tedious argument that the author doesn’t want to waste your time with. And I think this is a fair characterization of even the use that the author criticizes here:

> When I moved to New York, I was very excited at first. It's an exciting place. So it took me quite a while to realize I just wasn't like the people there. I kept searching for the Cambridge of New York. It turned out it was way, way uptown: an hour uptown by air.

In principle, it’s entirely possible that pg kept a detailed diary of his attempt to find a community of intellectual peers in NY that compared to the one he found in Cambridge, and if you read the entire diary you would be satisfied that he carried out an exhaustive search. But even if that were the case (I wouldn’t expect it to be; who keeps detailed diaries documenting every opinion they ever form), that would dominate the length of an essay that was supposed to be about how cities work as focus hubs for specific types of ambition.

That’s not to say pg can’t be wrong about this point; it’s still a statement of opinion. What “it turns out” really signifies is that the author made a serious effort to investigate the question prior to forming the conclusion. They might be lying about that, but they can also lie about facts.

I guess I just consider it an insult to the reader’s intelligence to say that ‘it turns out’ is a particularly deceptive way to sneak in an unsubstantiated conclusion, because it’s not very sneaky. If I said “it turns out the moon really is made of cheese”, nobody would be fooled. If Buzz Aldrin said it, a few people might be fooled, but only because they already know he’s actually been there.

On the other hand, we routinely accept “it turns out” reasoning all the time, in the sense that we generally trust other people to come to conclusions that we don’t feel the need to audit. If I get labs done at the doctor’s office and it turns out I have high cholesterol, I don’t have a particular need to audit the lab’s methodology. You can’t rigorously audit all of the information in the world and if a writer you reasonably trust writes “it turns out” that X, you are reasonably justified in updating your certainty that X is true.