They auto-installed the app on everyone's phone, and auto-enabled this feature on everyone's phone. The feature sends my location to someone else when they are nearby and using the app. So even though I deleted the app, other people nearby could still receive information about me because I haven't disabled the default toggle I never opted into in the first place.

It's almost suspiciously malicious that they auto-enabled this feature and auto-installed the app for everyone at the same time.

Installing a new app onto a phone absolutely changes the phone. This app was packaged in an OS update.