> Not necessarily. Learning enough English to understand the UI is much lower level than being able to converse.
Exactly this. For example, I am learning German and have changed the language of my reading tablet's UI to German. That in itself is a useful learning tool.
Also "right click -> Translate to <x>" takes care of the UI automatically (in Chrome at least) but still doesn't solve the issue that English can not used to converse with the AI.
It's also the difference between active and passive command of the language.