The mediation business is trust business. Once they build a reputation then they can start manipulating cases to benefit their business too. In a case between a regular client and a casino which has good relation with the mediator [he supposed to have, because mediation is his business], I do not see how the mediator will not be biased too.
I agree with you here. The Mediation business is a trust business, and there is no guarantee that they won't sell their reputation. Once they build some reputation, Players used to trust them. What if they build a good relationship with the casino company and manipulate the report? There is no guarantee that they won't do that. I already suspect a mediation service of doing such. I can give you an example; the rest is up to you. You can judge by watching the pattern of how they do it.
A few months ago, A guy created a scam accusation against PlayBetr and Betcoin. Then the guy filed a complaint, and they chose a mediation service which was thepogg.com. The complaint thread is here:
https://thepogg.com/complaint/playbetr-non-payment/. The result was in favor of the casino. If you see the comment section, You will see only thepogg.com commented on this case, and The Guy who filed the complaint could not write his comment. The Casino itself didn't write anything as well. At first, the casino accuses the player is guilty of fraudulent actions in Sportsbetting. But, Thepogg.com said the player is guilty of multiple accounts.
I am not saying they Manipulated the result. But, It was my assumption based on the case.