AI tends to really like staccato writing, a series of sentences that are too short and simple. It's evident here, although broken up with really long sentences.

Tortured and near-miss metaphors are another thing it likes and it's loaded here. "groaned like a drumskin too tight for the heat" sounds cool but then you think, do drum skins "groan"? And what does heat have to do with it? Or "breath of hills holding their heat like a secret", are they holding the heat or breathing it? At least for me there's the tendency to at first feel like I'm reading something really clever, words that are really tuned and carefully chosen, and then to start feeling like I've been pranked.

Ultimately I don't think there's any way to really be sure though, whether it's AI or just a human but annoying style. This doesn't really read as what GPT would typically drop from a basic writing prompt though, I would guess it's heavily prompted on style or reworked repeatedly.

FWIW though I experiment quite a bit with AI writing for fun, and I think Opus writes pretty nicely in its default voice (prompted mostly for content with little guidance about "how" to write). I'm an engineer so I don't know if real literary connoisseurs would see the slop right through this, but it's coherent, well paced, a little heavy on similes and metaphors but they land unlike the linked passage. Just a sample:

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Off the port quarter, the darkness lights up orange in a rolling line, gun by gun, and the sound arrives a full second behind the light.

Broadside.

Most of it goes over — a ripping, tearing sound in the air above, like heavy cloth torn by God. Two don’t. One takes the bulwark forward and turns eight feet of oak into a spray of splinters a foot long. One goes into the hull at the waterline abaft the fore chains with a sound you feel through your boot soles, and the sugar barrels in the hold scream as they shift.

A man is down by the foremast, shrieking, and another is not shrieking, and Homer is already running toward both with his hands out.

And Micheal is still aloft.

He’s on the fore topmast crosstrees with the stay gone under him, forty feet up, hanging off a spar that is swinging in a fifteen-degree arc and thumping the mast each time it comes back. You can hear him from the deck. Not screaming. Talking — fast, high, unbroken, reciting the rules to himself. "Touch wood don’t whistle don’t whistle spit to leeward—"