yeahhh that's probably because that myth isn't ABOUT Athena. It's about Minerva. No, the Roman and Greek gods are not identical -- the Romans put plenty of their own spins on them.
The definitive, well-known version of the Arachne myth comes from the Roman poet Ovid. No written attestations about a contest between Athena/Minerva and Arachne predate the Common Era. There's a Greek jar that *might* be a depiction of the contest that's from several hundred years BCE, but could also easily just be depicting Athena teaching weaving to mortals.
The Arachne myth MIGHT have come from ancient Greek sources that simply haven't survived, but it could just as easily be a Roman invention. And more to the point, the one you're referencing -- the definitive account by Ovid -- is written by...y'know, Ovid.
Ovid had a big anti-authority streak (the emperor Augustus exiled him so like, fair) and often emphasized the follies and unfairness of the gods in his writing, and he likely embellished some stories to make them look worse on the gods. Fdor example, he's the main reason we think of Poseidon (actually Neptune in his account of course) as having raped Medusa and Athena (actually Minerva) cursing Medusa for it. Before Ovid, there was little indication that Poseidon and Medusa's coupling was nonconsensual, and Medusa like her sisters was born a monster rather than cursed. Likewise it's entirely possible Ovid embellished these aspects of a pre-existing myth of Minerva and Arachne.
(also I feel like the Arachne myth actually makes Minerva look way better than the Medusa myth. The Arachne myth ends with Minerva regretting her decisions! She doesn't turn her into a spider as a curse, she does it to bring her back to life!)
So yeah, like. I guess my main point is we gotta remember that these ancient myths aren't actual historical facts about real deities. They're stories made to convey ideas, and oftentimes those stories come to us through specific people, and those people have Opinions about what they're writing about. The ancient Greeks didn't worship Athena IN SPITE of her driving Arachne to suicide (wasn't Athena) (they didn't have that story) (didn't happen it's made up), and in the same way modern versions aren't like, selectively ignoring Historic Facts about the gods. They're engaging in the time-honored tradition of reinterpretation. You can't ignore facts that aren't facts. There is no consistent Greek mythological canon -- and again, even if there were, Ovid wouldn't be part of it!
