The point is that the tools for prototyping, simulating, assembly, and manufacturing are becoming much cheaper. Along with the fact that people are sharing more.
I agree that there is no substitute for RTFM. That will always be required. Although, it's layers of abstraction in hardware too. Just like software libraries and frameworks: if someone has published a circuit that includes some subsystem I need, I can very likely ctl+v much of it into my own design without having a full understanding of it. Which is the entire reason why an industry around ICs can exist at all. It's just that more people are sharing now than ever before.
Pick and place machines are now becoming accessible at low cost (see Fire Pick Delta/LitePlacer). This addresses many of your assembly errors and mitigates costs.
I can't construct a reasonable argument against your points E, F, and G, which seem to all equate to "something unlucky and magical happened that broke your prototype".
If it's a hot hardware area (past hot areas: graphics chips, microprocessors, WiFi chips, OC-768 networking chips, ...), nobody will wait for the FPGA prototype. You get funding, you go to VLSI and maybe you produce an FPGA board for validation along the way. Probably not since what you're doing is probably too complex for a single FPGA anyway.
Otherwise, your volume is too small and the FPGA IS your product.
And that's only if you can't somehow make it run on a microprocessor.
The only place I've ever seen an FPGA validation board was with RF startups in the cellular space. And, even then, it was way back when the protocols were much simpler.
tl;dr If your demo doesn't run on a microprocessor (or SoC), it doesn't exist.
I agree that open-source hardware is not nearly as easy as open-source software. But I think it's definitely going to be both more open and less expensive.