The accusations are incredibly clear/defined (and serious!) and have a very simple burden of proof. These things either happened or they didn’t, and they have material evidence or they don’t. It’s incredibly unlikely that they filed such big, concrete accusations without concrete proof to back them up.

And while I am far from an Apple fan boy, yes a lot of big corporations file frivolous lawsuits but Apple typically does not engage in that behavior against other companies. Also bear in mind that open AI is a huge name so there is a public/political element that goes along with this for Apple. There are going to be a lot of people who do not want Apple to win this regardless of how true their claims are and will figut like hell to protect openAI