> But the short wires in a Nikon camera are not long enough to be a useful antenna. […] Everything is probably just traces on a PCB.

Anyone who's had to get newly developed hardware through EMI certification in recent times can tell you that it's quite easy to accidentally make PCB trace work as an antenna. Not necessarily a great antenna but enough to emit some random signal and fail certification. 3 GHz is 100mm in wavelength, and a quarter wavelength makes one of the simplest antennas… that's only 25mm. The whole story is much more complicated but the thing is that the scales are in range.