> if it was framed more as fiction

At some point, however fact-based, every speculation is a form of fiction, so the line is blurry ...

> The title and the abstract suggest they take this possibility seriously, which is ridiculous.

... but I'd say it's I think the idea is to take some serious and very realistic bits that have a vanishingly low probability ...

> We show that 3I/ATLAS approaches surprisingly close to Venus, Mars and Jupiter, with a probability of ≲ 0.005%

... and then walk from there as rigorously as possible.

As they say, "largely a pedagogical exercise".

There's still a line between the hardest hard sci-fi story about a Boltzmann brain and a fact-based thought experiment computing probabilities for a giant marshmallow to spontaneously appear in the vacuum of space.

Rama by Arthur C Clarke is a work of fiction, there's no blurry line there.

> We show that 3I/ATLAS approaches surprisingly close to Venus, Mars and Jupiter, with a probability of ≲ 0.005%

a) What does this even mean? If you throw a dart on a dartboard, anywhere it lands will have some probability. 1/200 doesn't seem that low.

b) It's the height of intellectual laziness and chicanery to go from not-that-low-of-probability to 'aliens'

They're free to make these claims. I'm also free to laugh at how ridiculous it is.

Now, if this thing had some précise shape, or rotational speed, or we saw it adding or subtracting delta V, or if it did gravity assists from multiple planets (not just 'flew kinda close to a couple of them'), now that would be interesting.

I'm actually unsure what you mean - what is that line? Why aren't both just exercises in probabilistic reasoning?