It is a coverup. Apple is overtly and completely aware of the optics surrounding photo scanning - they know that an opt-in scheme cannot work as they found out previously.
Since they cannot convince users to enable this feature in good-faith, they are resorting to subterfuge. We know that Apple is vehement about pushing client-side scanning on users that do not want it, I do not believe for a second that this was a mistake or unintended behavior. If this was a bug then it would have been hotfixed immediately to prevent the unintended behavior from reaching any more phones than it already had.
Exactly. It is absolutely bonkers that people are claiming that Apple is trying to cover up something for which they have a settings toggle and public documentation.
Yeah, we might quibble about what the default value of the toggle should be, but them adding settings for minor features like this is absolutely a good thing, and very much a sign that they're not trying to hide things.
If anything, the lesson Apple might take from this could be "adding the settings toggle was a bad idea, because nobody would have cared about this at all otherwise".