Interesting. I was aware that this new API exists. I've not seen an app use it yet. I was not aware it could narrow the selection down to just a single contact property. The documentation does not make that clear.
Nevertheless, apps like Facebook aren't going to use this as they want the whole address book and not a single person.
IIRC android has this too, it's just that it is seldomly used on both platforms because it is inconvinient (imagine having to select all contacts and search from them individually in e.g. WhatsApp) and means the app can not mine your data.
https://developer.apple.com/library/prerelease/ios/documenta...