No, it means that projects go faster and better when the most talented and most authoritative person is overseeing them. Anytime a large customer with urgent priorities or projects needed something from us, they'd ask if the key person would personally drive the effort. If it's a enough of priority, that would be the CEO, CTO, or VP Engineering. This is common in tech, but I assume for any other industry as well.
In Tesla's case, Elon is effectively all three. He doesn't *have* to drive the new product, but doing so will increase the likelihood of greatest success. In Elon's mind, anything less than 100% is not an option.
Edit: It sends a message that this is a kickass project that the top engineers will want to work on. The best devs want to develop, not to be managers. Elon driving your project is exciting because it means you're working on one of the most important projects in the company. All eyes are on your team, and you have a chance to show everyone what you can do. Demotivational is the opposite of what happens when Elon personally takes charge of a new project.