“Interestingly, this effect cannot be explained by differences in participants’ experience with generative AI models, as that variable is insignificant in the mode”
When predictors are correlated, which is most likely the case here, this analysis cannot separately estimate their effects. The software will end up splitting the total effect size between the two predictors. Without describing collineariry between predictors, it’s not possible here to judge whether experience with AI is truly unimportant or the analysis is merely incapable of spotting the effect.
As for eroding confidence in reviews, this will make it worse, but I already put next to no stock in user reviews anymore. You don’t need AI to make a good human-like review that lies about a product, and there are plenty of those around.