Good point. Many innovative projects (roads, bridges, etc.) were built by Roman army engineers who, while not necessarily elite, were certainly educated and could record their methods. So yes, innovation in areas pertaining to the military advanced much faster. What's surprising though is that improvements in steel production would have produced far superior weapons and therefore you think would be something the Romans would put a lot of effort into innovating on. I'm guessing that blacksmithing wasn't the type of grand project that required oversight/planning by educated army engineers. Or perhaps the hardness of the Roman swords and spears didn't make much difference compared to other military factors (discipline, tactics, defenses, etc.)