Yes, I agree that without actual data on specific installations, it is just speculation. If you’re concerned, you do the tests. My gut feeling is that you shouldn’t just take it for granted that it won’t be an issue. Even if it only attenuates the RF by a dB or so, or less, that might mean the difference between losing your rocket or keeping track of it - all for the sake of a pretty paint job.
Faraday shielding will probably only be significant if the ‘mesh’ dimension is less than roughly 1/10 of the wavelength of interest; the shielding is completely surrounding the electronics; and the shield is at the same potential as the electronics ground.
At 1 GHz the wavelength is about 30 cm, so 3 cm represents the maximum ‘mesh’ dimension here. Any metallic particles in the paint are likely to be significantly closer than that. So, the potential for shielding to occur could be real. However, given that the metallic paint coating will most likely be electrically ‘floating’ with respect to the electronics inside the nosecone or body, then there is the possibility that it might act as a passive re-radiator, rather than a Faraday cage.
Also, given that the metallic paint coating does not completely surround the electronics, then there is plenty of opportunity for RF to get around the ‘shield’. It will completely depend upon the particular installation.
I haven’t performed any tests on RF shielding in a rocket, but I have performed bench tests on the effects of metallic components adjacent monopole antennas inside avbays. The presence of metal conductors near the antennas does indeed effect their impedance and resonant frequency. I posted some results of these tests in another thread on TRF perhaps a year or so ago. I will endeavour to repeat them with a metallic painted enclosure and include some attenuation measurements.