The article isn’t arguing against requirements existing, it’s arguing against being bound to de facto requirements because you allowed a client you don’t own to

The article isn’t arguing against requirements existing, it’s arguing against being bound to de facto requirements because you allowed a client you don’t own to depend on behavior you didn’t specify. (See Hyrum’s Law: https://github.com/dwmkerr/hacker-laws#hyrums-law-the-law-of-implicit-interfaces https://github.com/dwmkerr/hacker-laws#hyrums-law-the-law-of...). By limiting the scope of unspecified behaviors, you also limit the scope of what makes for a de facto breaking change.