It's using a couple textbook [1] LLM tropes, 'negative parallelism' with a 'here's the kicker' tone.

[1] https://gist.github.com/ossa-ma/f3baa9d25154c33095e22272c631...

But it is specifically one of Claude's ticks

I'm guessing he means overall the kind of circling and concluding that Claude does, like "the actual truth is more interesting than it seems" or "the real smoking gun is not the x, it's the y that was under our noses all this time" type of writing.

While AI was clearly used to generate and structure a first draft, I say it has been extensively rewritten by the author. In my experience, AI tends to avoid the first person, instead writing from a passive observer or even using sentences without verbs. The length of the sentences is also more natural. AI had trouble with bind-words in an argument. It just states separate facts and assumes because they are stated in order you have a reasoning. I'm not seeing that here.

Of course, idioms are preserved, and not everything is rewritten.

I quite ok with this style, it isn't grating. I expect this will be a style we'll see more of in science.

This phrasing is a very specific "Hello, this is Claude"

The whole thing is clearly written by Claude.