No shit. The fact they only discovered that once they've got burned proves they never even questioned what generative AI does.
Though I'm sure half of the blame is from them asking it to tack the most clickbaity headlines on every article they can. Even human editors all but outright lie in those, of course an AI is going to hallucinate you the best title it can.
The article doesn't explicitly state it, but the wording implies that this headline was not created by BBC. This appears to be a service running on Apple products producing its own summary of the news article. So the BBC didn't get burned by something they did and that's what they're complaining about.
That's the BBC criticising Apple for indiscriminately mangling all notifications with AI, like news headlines. The BBC could boycott the Apple platform, but that's basically their only lever to stop Apple doing this besides asking nicely.