I don't see how that's "sharing of info" - it's your info to begin with, it doesn't get shared. The "Siri" search features on your device recognize potential calendar events, contact info, etc., in mail, messages, etc., and ask if you want to add them to your calendar, contacts, etc. It's not happening in the cloud, it's happening right on your devices.
So, on Mac: System Preferences > Siri > Siri Suggestions & Privacy.... - You'll be able to disable/enable suggestions on an app-by-app basis.
I don't see this as violating an "illusion of privacy." Just the opposite. Features of this sort do what a personal assistant might do, if I had one. Only, instead of having some employee privy to everything I do (and trying to anticipate my needs), it's a machine that has no consciousness. It's designed to not share my info. So overall, I get a small thrill from these things.
But different strokes for different folks. Over on iPhone models with Face ID there's something called "Attention Aware Features." It's an application of the basic Face ID functionality - Face ID is designed to recognize when you're actually looking at the screen, so that it doesn't unlock simply because your face comes into range of the cameras and sensors. Once the capability existed, other uses became possible. For example, if the phone starts ringing, as soon as you look at the screen the ringer will stop ringing (this can be disabled in Settings > Face ID & Passcode). After all, once the ringer has your attention, why does it have to keep making noise? I'm sure this was invented at some engineering meeting at Apple - someone who forgot to silence their ringer in advance was embarrassed by the interruption. I love this, but I know others who are totally freaked out. After all, traditional phones just keep ringing and ringing until you actually answer the call. A bell that goes silent before you answer? Just creepy!
Some people are disturbed by machine "intelligence," others are delighted. And so it goes.
