But while they may seem unusual, Steam labels like the ones for Denuvo Antitamper are nothing new. A high-scoring thread that appeared on Reddit suggested otherwise.
A similar label for SecuROM DRM appears on the Grand Theft Auto 4 Steam page; Trackmania Turbo's Steam page has a label sign-posting a required Uplay account; and there's similar for Rockstar Games Social Club accounts on Grand Theft Auto 5's Steam page.
These labels are simply fields that can be filled in in Steam's backend by whoever creates the page for that particular game. Denuvo's marketing director Thomas Goebl explained this to me in an email. He even sent me a picture of what the backend looks like, um, so to speak.
Still, I hadn't noticed it before (as if that means anything at all).