Yeah red eyes b. Chick is not part of the archetype. This is not unique Harpie’s Brother for a full name errata to remove his association with the Harpie archetype.
I mean, this won't be the first time something like that happened. Des Gardius and B.E.S. Big Core has a PSCT that doesn't exist in TCG yet, and Forbidden Graveyard is already changed into Silent Graveyard a few weeks before TCG reprinted the card. And they updated Gilasaurus' PSCT.
Now the question is why they still haven't errata Red-Eyes Spirit and Paladin of Dark Dragon in DL.
There isn't really a reason to errata cards to remove card names that no longer exist. It doesn't actually functionally change how the card works, and updating its text in the database is meaningless, since it doesn't magically make RL copies of Pothole Squad update.
Also, fun fact: Warrior of Atlantis names a card that doesn't exist as far as the game's concerned, and isn't due to a name change.