I ran a hardware startup for about a decade. We ended up doing all PCB assembly in China. We did try to find this in the USA, but it was indeed too slow and expensive.

The bottleneck in assembling a PCB is usually component sourcing. My product was not the most complicated, and even then, to assemble in Shenzhen, China, it often took a few weeks to get all the components.

The core issue here is that latency is determined by the outliers. Assembly can't start until you have all units, and the hardest to source one is the bottleneck!

To me, the core innovation here is to plug into the design software to source these long tail items ahead of time.

It's pretty interesting that usually when the PCB is being designed, the designer has no awareness of supply chain. They'll bake in a chip that has a 4 week lead time without even realizing it, when a similar component might be one cent more expensive with much faster lead time.