I recently got a new iPhone. As a part of setting it up I synced my photos from my PC to the new iPhone (as I did with the old device). After that, I waited for the phone to run it's face recognition. What surprised me was that some people got named correctly by the new phone (I provided the names to the old phone). I thought face recognition only runs locally. Both phones have iCloud Photos, My Photo Stream and Shared Albums disabled (the new phone had it enabled by default, but I switched it off in advance of syncing the photos).
Edit: The old phone was the first iPhone SE, the new one's the second generation. Both are running the newest iOS versions.
I was under the impression face recognition feature respect the users (and more important the users friends) privacy and is not crowd sourced and only exists on my device.
How is this possible?