If they see people getting the worst experience while playing gambling on their site, the team will contact and ask them further.
You do not have to believe everything from the review site but that can be your information to research for more.
The important is how you can collect any info about the site from many sources and the review site is just one of the sites that serve the information.
If you make one customer who has a complaint end up being happy, they are making only one customer happy and that's it, but when they change the whole system that caused that complaint then they are preventing god knows how many people to be complaining about the same thing. This is why I honestly believe that there is a good case for figuring out trustpilot cases to be not just one case, but a whole systemic situation.