Most of the comments (all of them that I've seen) say that the effect is real, but the source isn't necessarily a bias in the reviews, because of how the study

Most of the comments (all of them that I've seen) say that the effect is real, but the source isn't necessarily a bias in the reviews, because of how the study was conducted (eg, there could be a hiring bias). Bringing up a different cause to explain an effect is not dismissing the effect as existing in the data, merely calling in to question the source of it.