Missing NPCs -were they removed?

[An Ning]

So while looking for information on what we might not have completed, we came across a list of NPCs, and I couldn't help noticing that some of them seem to not exist.

In particular are Nina the Farmer, who is supposed to be in Lunar Landing (all my map shows is 1 NPC present, Mr Teeter, there are no other indicated NPCs, not even the "???" mark), and Rigolph the Alchemist, supposedly in the Sea of Stalks (same).

Were these NPCs moved somewhere else, removed from the game, or are they hidden and they only show on your map guide after finding them?

[Fulano]

If I remember correctly, they only show up on the guide after you find them.

There is a small chance they didn't get added to the map when it was created, usually with small maps but that's very rare.

[An Ning]

They show up as a name after finding them, but prior to that, they exist as a "???".
My maps aren't even showing that, for these particular NPCs.