Well I don't think the position of planets when you're born has a large correlation to how your life will go.

On the other hand, how an AI writes will have a big correlation to whether the written text would likely be written by an AI.

The latter is more of a direct relationship.

Maybe A and B are not correlated, and Y and Z are? What pattern are people falling for here?

It's not really about the planets. It's about what other people believe about the planets.

You could work for a boss that's a Leo, and he/she believes only Leos deserve to get promoted, or that Leos and Scorpios should never be assigned together on a shared project. Your life and career trajectory under this boss could be totally different, depending on whether you were born a Leo or not.

Certainly "not all bosses" applies, but it's not really that farfetched or uncommon either. The point is that a correlation does exist, but it's a social one and not a physical or astronomical one (and it's also often a self-reinforcing/self-fulfilling one: Leos who read what astrology says Leos should do, may end up choosing to behave more like that).

So in the LLM example, it may not really matter much what physical markers of provenance or physical correlations there are, as social beliefs or perceptions about suspected provenance may be the strongest correlation anyways (in terms of impact and outcomes).