It's very simple. You want to upload images to iCloud? Then let your phone scan it and upload it. You don't want your images scanned? Don't upload them to iCloud.
As skinkestek kindly pointed out, the point of my sarcastic comment was that now that the precedent of scanning the contents of users’ devices - as opposed to the contents of Apple’s servers - has been set, deciding whether to do so based on the state of a single “Store photos in iCloud?” toggle is going to start looking awfully arbitrary.
