fake pcbs are cheaper to produce than a real one while giving near identical looks and weights to a finished product. its commonly done for testing or sales purposes everywhere in the world in any place that a pcb exists military or not.
phones in a phone shop for example are usually dud systems or severeley cut down in circuitry for demo purposes only
bro… guess what, making a PCB LOOK the same as a real one, does not mean you made a REAL PCB. fake ones ditch the solderings, many of the internal connections and capacitors and resistors
photolithography. pretty simple stuff that you can do in a shed. however adding capacators and chipsets still costs more than a bare board for a mockup
to give an accurate weight to information brochures while being cheaper than a fully complete product
Military expo shows do have a lot of press or random civillian punters yes but they are not selling to them, they are selling to the militaries that are checking things out there. they arent going to pay attention to something that looks like an empty shell.
Its a matter of presentation over its actual function, ill use an analogy i used higher in the thread
You just need to show something basic but preferrably looking functional to get attention to possibly put a sale into motion