Man do not go just to statement just to win an argument, both aircraft the F-35 and J-20 have the same continous curvature and diamond shaped cross section to reduce radar signature is that okay? well the area exposed by the J-20 is larger, it reflects more electromagnetic waves than the F-35 therefore its radar signature will be larger on equal RAM coating, if the F-35 has inferior coating might be equal.I see a flaw in your thinking. You think that more area equals more radar signature. So your saying that a smaller Mig-21 has a smaller RCS than an B-2, cause the B-2 is larger? Then what definition is stealth to you then?
Another thing, you have no idea how much the J-20 weighs, how big it actually is, its capabilities and performance, nor do you know how much thrust the engine outputs.
Now to answer your question yes the B-2 does reflect more radar waves than the MiG-21, the difference is the MiG-21 sends them back straight to the radar while the B-2 sends the radar waves away from the radar, so what a radar operator sees is 90% of the original radar pulse on a MiG-21 and just 0.1% of the B-2