Interesting, so this isn't a standard Android feature? My Galaxy S-series phones have been doing this for years.

See my other comment: https://news.ycombinator.com/item?id=40142394

If you give SuperFreezZ App stopper permissions (it needs to be registered as an accessibility service, and requires usage access as well) to check for usage of applications, then it will freeze unused applications automatically. You can even specify after how many days of not having used them you want to freeze them.

Samsung's Android flavour removes permissions from unused android apps automatically, and sends a notification to let you know. Close enough I guess.

fwiw this seems to be partially in place already.

Requests for access to files, location, mic, and camera usually give me the option of allowing them all of the time or only when the app is open.

I've also noticed system notifications stating that permissions will be used from unused apps.

Greater configurability is always nice though.