Privacy policy URL for app

I've read through Apple's policies of whether or not to include a privacy policy URL for my app and i'm still unsure.

If you're currently NOT signed into GameCenter App or in Game Center in Settings App and you open my game app there will be a Game Center sign in pop up. If the user signs in, since they can sign in using my App, do I need a privacy policy URL for this?

I have Facebook/Twitter share buttons in my app. If the user is not is NOT signed into Twitter/Facebook App and when they go to my app and click on Facebook/Twitter buttons they can not sign in via my button in my app. They must sign in the facebook/twitter app. However, once they sign in the Facebook/Twitter app and now go into my app and click the Facebook/Twitter button. They can post whatever information they want inside the button and click POST/SHARE then that information will be posted on their Facebook/Twitter accounts. Do I need a privacy policy URL for this?

According to https://developer.apple.com/app-store/review/guidelines/#privacy you only need a privacy policy if your app has account sign in capabilities.

17.5 Apps that include account registration or access a user’s existing account must include a privacy policy or they will be rejected

If your app just links to other apps and they handle the sign in, you should be clear without needing a privacy policy. You could also rely on iOS to handle the account log in - same release from the requirement is met in that case.