The clue to it all is in the word "terrestrial"
To trained planetologists (and self-taught geeks like us), its a classification for a planet of rocky composition. Metallic cores probably enter into it, too -- atmospheres don't.
To the untrained -- which sadly includes a lot of journalists "stuck" with interpreting science news for their general readers -- terrestrial = "Earth-like". They focus on the "terra" part, and without remembering (or ever knowing) that Mars, Venus and Mercury are also terrestrial planets, they inadvertantly allow their readers to think of another cool blue planet, with water in all three phases.