Comment by Tuna-Fish

The reason he was so skeptical is that for other engine manufacturers, there are generally different teams working on different parts of the engine, and because Convay's law the final artifact generally ends up looking like the organizational boundaries of the company that made it, with cleanly separated parts for every sub-organization that you can see in the final assembly. One of the things that SpaceX is good at is optimization across these kinds of boundaries, integrating hardware in ways that would be difficult for a more traditional organization.