There's a somewhat better discussion of this phone here.[1] At least the making of the board. Board manufacture, SMT pick and place, and soldering are all automated, and the equipment is widely available. Everybody does boards roughly the same way.
The assembly problems in phones come from all the non-board parts. See this iPhone teardown.[2] Look at all those little subassemblies. Some are screwed down. Some use elastic adhesive. Some are held in place by other parts. They're connected by tiny flexible printed circuits. That's the labor-intensive part. Usually involves lots of people with tweezers and magnifiers. They don't show that.
So here's that part of assembly in a phone factory in India.[3] Huge workforce.
For comparison, here's a Samsung plant.[4] More robots, fewer people. Samsung made something like 229 million phones in 2024. If a US company produced phones at Samsung volumes, the price would come down.
[1] https://puri.sm/posts/manufacturing-the-librem-5-usa-phone-i...
[2] https://www.ifixit.com/Teardown/iPhone+13+Pro+Teardown/14492...