What makes anyone think the J-31 would be anymore useful against the F-35 than the J-15? I've seen no evidence the J-31 would be any more effective than the J-7 against F-35.
Following You posts in this regard since some time, may I ask if You are blind or is there another reason besides Your bias and hate ???
I know that for You the F-22 and F-35 are the crown jewels in modern aerial warfare - and they are surely so - , but to compare the FC-31 (even as a demonstrator) with the J-7 is either plain stupid, provocative or indeed "blind", which would explain why You "don't see any evidence"!
I do not want to say the FC-31 or J-20 are hyper-super Raptor killers, but at least a more balanced view would help in these discussions.
Deino