Yes, it was mostly this. The sharp credentialed engineers could design, model and simulate complex systems like nobody's business. But, of course, models are ne

Yes, it was mostly this. The sharp credentialed engineers could design, model and simulate complex systems like nobody's business. But, of course, models are never quite exact representations of the real world, especially when it comes to hardware. So the engineers with pracitical knowledge would look at the hardware and (usually rather quickly) spot missing decoupling, debouncing, metastability, sneak paths, etc issues.