Machine learning is literally a numbers game. The bigger and higher quality your data set, the better your models. So, it's contradictory that a company like Apple assuming they've taken a "privacy first" stance, can also simultaneously claim to be a competent player in this machine learning arena.
The other thing is, it's really tiring to see "Apple is a privacy first company" narrative on HN. Because, nobody knows exactly what Apple is doing behind the scenes with your data. There's literally no way to know what Apple is upto other than trusting their marketing material that claims to be privacy centric.
For all you know, they could still be doing stuff what other companies are doing secretly and nobody can prove nor disprove that. Next, iOS is closed source. Without access to source code, this privacy narrative is nothing more than just a marketing gimmick. We're a tech crowd and we should definitely take it a step ahead, investigate and then conclude, rather than blindly believing marketing posters that Apple puts out.
Once your data moves to a private cloud like iCloud, there's no way to guarantee anyone's privacy or safety for that matter other than blindly trusting the vendor. Don't believe me? Ask Jennifer Lawrence.