[fsloth]

Simple:you can't scale an engineering effort witout limits. However, you can have as many parallel engineering efforts as you like. They can cross pollinate ideas as much as they want to, but it's very hard to share parts of the process unless they are mundane components that can be outsourced.

Openness in itself is not bad but is not a requirement for unique engineering. See what Lockheed's Skunkworks did with SR-71 for example.

They boosted on decades of aeronautics research and individual talent - these provided the raw materials. They then combined these to reach the specific design intent.

In short: you can share a theory but not a chain of command or process without costs of then having a process to control this sharing.

It's also much better to have parallel vehicle designs at this early age of our space efforts than pour everything into a single megaeffort.