Ask HN: Apple iOS “maybe” suggestion on phone numbers

Does anyone know how Apples feature of suggesting who a number you do not have in your phone book might be? I only thought it was from searching through emails locally.

I am a little bit worried seeing a suggestion today. I have a co-worker who's number I already have in my phone book who has written a message to me and another colleague whom I do NOT have in my phone book. But it correctly suggested that it might be my colleague.

This is on my private phone and I have no email from the one Apple guessed in my inbox, the only thing I have is a LinkedIn request from him, but that does not contain his phone number - so how in hell do they suggest it being him? I only thought it looked locally on my phone, but I cannot in any way see how it should find information on my phone linking that phone number to him.

The only way I can find that connection would be if they had it from potentially his iCloud account - but I would hope that they did not transmit that information. Or could he actively had selected to transmit that information?