It's a wonderful un-process hack. You talk about tooling, but there's also just so much less process, so much less variability, so many less joints & non-uniformities. It may be slow, but you only really have a limited set of lessons about printing to learn.
By compare, look at videos comparing Starship nosecone over time. So much rocket building is a manual process, and it's hard work figuring out how each thing has to happen. I think even the cylinder fab has a lot of lessons that have gone into it.
At first this kind of felt like a gimmick, but being able to go deep on one ultra-flexible thing & reapply those lessons again and again seems divine. Being constrained by chiefly imagination, asking only where you want to put material not how you want to get it there is such an enormous liberator.
And once it's working well, they have such deep parameterization tweaks they can make, to optimize hone & refine. Thin this in this area, try some different reinforcement patterns on this wall... having a totally abstract way of building feels like cheating, it's such an obviously easier better freer constraint-less way of making real.
The potential savings here seem to more than make up for a potentially slightly slower build speed.
Falcon 1 and electron are smaller vehicles in addition to being not 3D printed.
They had the runway and investor confidence to attempt a larger vehicle as their first