Not knowing about the ability of it to do that is not evidence that the ability doesn't exist. You were already trusting them not to do this before, since they

Not knowing about the ability of it to do that is not evidence that the ability doesn't exist. You were already trusting them not to do this before, since they had full access to the texts and images as the developer of the app. The development of systems that can recognize these kinds of images predates this and you likely have been previously aware of them already existing and the ease of deployment of them. Trust of Apple is already all that stood between them being abused and them not being abused. I don't really understand what argument is being made here.