People you know
Contacts are a decision. Connecting Gmail, Messages, or an address book should not quietly invent rows on the list you keep.
People you know is the holding place. Everyone those sources can name shows up there, merged, while the grid stays the list you actually filed. Drag a vCard in: they land with the rest of the people you have not decided on yet.
Companies get the same treatment. If a domain keeps showing up around people you talk to, it appears in Companies you know — still latent, still yours to file.
The doctrine does not change. Nothing auto-creates a contact from a CC, an iMessage, or a LinkedIn URL. The import can be loud. The list stays quiet until you say so.
Improvements
People you know
One sheet of everyone found in mail, messages, and the address book, with no cap on the merged list.
People you know
Lives at /contacts/suggested. A banner reports how many new people showed up while imports and syncs run.
Companies you know
Organisations behind the people you talk to, the same latent pattern as people.
Import
vCard drops land in People you know, not the grid. Contacts stay a decision.
Fixes
Gmail
Messages without a To header are treated as having no recipients, not as a failed sync.