Mac OS and the stream
The Mac OS 9 reference is not a costume placed over a social product. It is a way to make the interface explicit, friendly, and easy to read at a glance.
Windows and context
Title bars, status bars, borders, and small controls tell the reader where they are. The feed remains the main object; the chrome gives it a frame and a sense of place.
Less hidden state
Birds keeps Topics and About in the rail and leaves presence, follows, and notifications for a later conversation about real use. A calm first version is easier to read, easier to maintain, and more honest about what the product does.
Retro as product language
The reference also gives the product a memorable identity. Birds can feel like a distinct environment without abandoning responsive layout, readable typography, or the ordinary WordPress pages beneath it.