The claim here is that the Figure 2 and Figure 6A look like they separate blot, but if you look at the pixel level shape of the dark blue highlighted bands, you'll see they are the same band. I.e. the bands being used to say that the mock in Figure 2 had no effect on p-IkBa are the same bands that are used to claim that the mock in what is presented as an entirely different experiment had no effect.
You might argue that they have demonstrated that mock treatment has no effect once, isn't that good enough - but in that case, why present it as though t were a different experiment? Its not just that they are presented as though they are on the same membrane, but also look at the columns -
Bands in the same column are supposed to have come from the same physical sample - the same membrane probed with a different antibody. Both Figure2 and Figure6A have been probed for both p-IkBa and p-JNK, but where as the bands for p-IkBa are the same across blots, the bands for p-JNK are different. That suggests that in at least one of the figures, the bands for p-JNK did not come from the same samples as the bands for p-IkBa.
As for why this wasn't spotted- this stuff is pretty hard to see unless you look really carefully for it - examine the deformities in each band, where are the dust grains (e.g. in the fourth IkBa band there is a black bulge on the top of the band about 3/4 of the way along). I wouldn't have seen this unless someone had told me it was there.