A product can work perfectly and still be unusable. UX is the difference.
Before “UX” was a job title, Donald Norman and Stephen Draper’s 1986 User Centered System Design argued for a specific discipline shift in computing: design should start from what a human actually needs and how they think, not from what the machine can technically do and then hand the person an interface to cope with it. That inversion — user-first, not system-first — is the foundation of what later became formalised as user experience design.
This essay’s own instinct tracks the same logic: “the challenge is building the appropriate knowledge base and user experience” is naming UX as the second hard part of an AI product, right alongside the knowledge base — because a client-facing AI tool that technically has the right answers but is confusing to actually use will still fail in practice.
Source: Norman, D.A. & Draper, S.W. (1986), User Centered System Design: New Perspectives on Human-Computer Interaction, CRC Press.