That statement contradicts Whatsapp official statement that all content is end-to-end encrypted: “WhatsApp ... we built end-to-end encryption into our app. When end-to-end encrypted, your messages, photos, videos, voice messages, documents, and calls are secured from falling into the wrong hands. Only you and the person you're communicating with can read what is sent, and nobody in between, not even WhatsApp.”
In this case, I believe Whatsapp more than I believe a technically illiterate writer on a government website that failed to understand some nuance. Maybe some Whatsapp users forwarded questionable content they’ve received to the authorities, then the algorithm scanned that content. That’s very different than secret scanning happening within Whatsapp.