Absolutely. I'd add that we also need
a privacy-preserving way to see that contacts have accounts on a given social app (aka contact matching).
A standard pattern for social apps is to ask for access to your contacts to see if anyone you know is on their app. This is important to creating a healthy and diverse ecosystem of social software, because these apps are really up against the natural network effects of existing offerings.
Contact matching is the best shot app creators have at bootstrapping new social offerings, but right now the experience sucks. Just to see if you like a new social app you have to either a) give up lots of private data in perpetuity to an entity you don't know, or b) have a subpar experience of manually finding people.
One solution may be for Apple to offer an API that helps social apps match users. Apple acts as the escrow system to match contacts so that the apps never have access to private contact data, and the apps just get notice when there's a new contact match to offer the user.
On the user side, the user has a simple privacy setting that says 'find matches once' or 'always look for new matches when app is open'. Users may also toggle whether they wish to be discoverable by others.
In a world with this feature, we get to try new social apps without concern, and apps only have access to an anonymized user ID for our contacts that are also using the app.