Quite a useful piece, CMil. It chimes with the Israeli report on F-35 that raised three main concerns,the first of which was:
A low radar signature in the X-band and Ka/K/Ku-band, the frequencies used in most current threats. This low signature is effective especially in a forward sector, but less so in other sectors. Its level of stealth is much lower against radar using lower frequencies (and the Russians are already developing such systems).
I would place the B-2's RCS at around 0.0001 m2 or -40dBm2 (head aspect so that we compare like with like compared to CMil's figure for the F-35). It appears that everyone here is using the US band designations, but to talk numbers, I would say that F-35 stealth optimization is in the 1.5 to (say) 10 GHz. There is a big difference between that region and large radars operating below 1 GHz, even down to 100MHz which would be classed as metric radar.
So, I would say that Bevo's comment regarding the difference between the secret RCSs of two very different aircraft would be difficult to dismiss, especially in the lower wavebands.