As an example for #2, when I got an Android somehow I was either automatically opted in or accidentally opted into location sharing. Two years later I found that Google Maps could show me every location I had been to for the last 2 years. I could review, day by day, everywhere I had gone, what time I went, how I drove there and where I went to next.

You can just mute the connected speakers and it's the same as having Siri off. Or get one of the ones that requires you to push a button (the Amazon Tap).

Many phones work the same way, the phone is always listening for you to say ok siri.

Can't you turn of this feature on iOS? I don't have Google assistant on on my device.

Yes, you can. It’s in Settings under “Siri”.