For industrials, examples are given as "aircraft, ships, machinery, electronic and electrical equipment". For durable consumer goods, the examples are "cars, furniture, televisions, washing machines". I fail to see the distinction between these two industry types. From what I can see the two groups are both manufacturers. Industials are involved in the "supply and production of goods" while durables are companies that "manufacture consumer durables". Is a television and a washing machine not electrical goods?
Yes, they are - they are relatively cheap, produced in high quantities and have a limited lifespan. Contrast these to other electrical equipment - radar, factory production lines, industrial washing machines etc. Such items are significantly more expensive, sold in smaller quantities and will be expected to last for much longer. It's a very different market, and one that will behave very differently to the consumer market in different economic circumstances.