The reason they didn’t know is because the AI groups aren’t the ones scanning the Internet, different projects do that and publish the data, and yet a different project identifies images and extracts alt text from them.
They’re probably freaking out about as much as any search engine is when they discover they indexed CSAM, and probably less because they’re not actually holding the images.
I know the point you’re going for, and raging out at the topic only undermines your point.