To be clear, this isn't exactly a new provision — Apple already required apps that offered subscriptions or interacted with Apple Pay to have privacy policies. As of 10/3, though, that requirement will apply to all iOS, macOS, watchOS and tvOS apps, regardless of whether they actually use or store your personal information. (Whether anyone actually makes it a point to read those privacy policies is another question entirely.)
Greater transparency in this case is a good thing, and we as users will be able to make better judgments about the apps and services we choose to use. For now, though, we're not sure whether Apple will try to actively police these privacy policies — after all, the company certainly has the power to pull apps or otherwise take developers to task if and when privacy violations occur. (We've reached out to Apple for comment, and will update this story should they respond.) Given the company's generally hands-off approach to managing the App Store — not to mention the amount of work needed for this kind of policing process — that seems unlikely.
Still, we now in an age where our data and the way it's used is subject to significant scrutiny. We wouldn't be surprised at all if Apple -- and the rest of the industry -- starts coming down harder on companies and developers that can't live up to their own promises.