An app can't listen to the mic unless you grant mic permission, unless the app has been bestowed with magic entitlements by Apple. For example, Apple Clips is an app in the app store with magic entitlements that bypass cam&mic permission prompts. I have no idea why they brought out the big guns for that. Also, Uber was running with a magic screen scraping entitlement for a while, apparently to support Apple Watch in the early days.