I'm not sure. IMO when you buy a Mac (or use Windows or an Android phone) you have accepted so much that there is nothing which is not allowed.

But nevertheless: as far as I have understood it everything is built on your computer and is still used on your computer. You - as the user of the Mac - has took and saved the information. Your Mac is then only working for you - if Apple doesn't load the information in their enviroment.

This is going to depend on the holder's relationship with the data subject.

If you send a friend an email, they may add you to their address book and set a reminder for your birthday while they're at it. They don't need your permission to do that, so why would a device acting on their behalf?

On the other hand, if a customer of mine asks for the data I have on them, do I have to send them my Personal Knowledge Graph facts about them? That's less obvious, and I'd lean towards Apple's helpful database being a liability even if it's local.

It's on the person's Mac so it is a little more complicated. The person you send your data to is the Data Controller, and fails you by not publishing their privacy policy. But Apple isn't a Sub-Processor here, because they aren't sending the data to Apple.

I'm saying that because I wish the GDPR also covered the software providers who perform Data Processing against the will of all parties, but it isn't the case. Lastly, they're a person and not a business.

It is however clear that building a database of people which may contain race, religion or political opinions is illegal, even if it's just a person doing it.