I am asking this question because, for me, there could be a possible conflict of interest here.
As a review site running its own gambling site, there might be a concern that they could potentially undermine their competitors on their website to boost their own standing in the competition. This could involve making biased or false statements to praise their own website.
While I'm not certain if this is happening in the real world, it raises the question of whether you would trust a review website in such a case.
I think in this case, there could be biase in judgement that is the casino could possibly review another casino in a bad bad just to promote their own casino. They can not be a judge in their own case so therefore, it is best they stick to their review or they face their casino business otherwise they are going against the ethics of professional engagement.
In some cases, they might even recruit reviewers to talk bad about their counterparts in strong competition with them just to discredit them and make them look bad ii n the eyes of gamblers with ill intentions of getting more traffic to their casino.
In all, I think it is unethical to engage in such because as a review site, it is expected that they remain neutral and fair I judgement as it relates to their activities.