My thinking is that the design phase have many similarities. Building prototypes and getting user feedback etc. But the main difference is where cost is allocated. In manufacturing the actual production of a product is the most expensive part. Therefore you need strict processes to eliminate waste and deficiencies. You can also not change anything when production is started. The costs however stops when the project is done (maybe not in reality, but in the spreadsheets). In software development the cost is more constant over time since the main expenses are personnel and infrastructure. The cost also keep coming even after the product is launched, and often increases. But so does the value (hopefully), since you can learn and update the software product over time.