Because then users could just disable anti-features. See https://faq.whatsapp.com/1217634902127718/ https://faq.whatsapp.com/1217634902127718/ They are trying

Because then users could just disable anti-features. See https://faq.whatsapp.com/1217634902127718/ https://faq.whatsapp.com/1217634902127718/ They are trying to make "unofficial" synonymous with harmful. Sure the article doesn't outright say that all apps are harmful. But it definitely doesn't make any suggesting that a third-party app from a trusted developer could be ok.