Why did they have to "un-learn" anything? What they should learn from that experience is that the particular tool they were using did not have a feature they e

Why did they have to "un-learn" anything? What they should learn from that experience is that the particular tool they were using did not have a feature they expected. Any reasonable teacher should explain that. It's important because often, extra features come at a cost and while some of those costs have been paid permanently by researchers and software developers of the past, others still require tradeoffs. Thinking in abstract terms is all well and good until you actually have to run code in a real environment to solve a real problem with the tools you have available.