He's saying that eventually when your feature surfaces as a UI the customer may not like it.
To which I have 2 responses:
1. not all features need a UI to be useful
2. this also demonstrates the infantilising nature of scrum where no developers can be trusted to think deeply, talk to stakeholders and otherwise do the right thing in a fully-rounded way but must just follow the exact instructions expressed
I mentioned UI because of the parent comment (about hooking UI up to a sub-component).
The core idea I was trying to get across is that until a feature is working and in front of a customer (or stakeholder), it's essentially in limbo because you don't know if you've built what they wanted. Maybe there was a miscommunication, maybe they find the feature confusing, maybe they've changed their mind. The goal is to get feedback as soon as reasonably possible.
eg: A stakeholder (or customer) requests feature X, and everyone agrees it's a good idea and we should to work on it right away. The dev team could spend 2-4 weeks writing excellent behind-the-scenes code that's not hooked up to anything, or you could spend 2-4 weeks on holiday. Either way, you've given stakeholder the same thing: No new feature.
If you're confident that you know exactly what it is you want to build then you don't need Agile, scrum or sprints. Scrum isn't supposed to be waterfall with arbitrary reviews every 2 weeks.
Customer is a poor term. It should be stakeholders. Sometimes the stakeholders aren't "customers" per se, they could be other parts of the organisation for example. I'd consider my CTO a stakeholder and I'm pretty sure he's interested in the value of fixes for a security audit or working database backups even though those don't necessarily have a nice demonstrable UI.
To which I have 2 responses:
1. not all features need a UI to be useful
2. this also demonstrates the infantilising nature of scrum where no developers can be trusted to think deeply, talk to stakeholders and otherwise do the right thing in a fully-rounded way but must just follow the exact instructions expressed