Why should they prove that there is no superusers though, I don't get it. Is this normal in a regular poker place (I've never seen one or even had one, just private poker with friends) that they have to let other people know the table they're sitting at are full of these superusers? I mean, if it is a former employee, then shouldn't they not even be allowed?
I also had the same question as you when reading OP, but
Lakai01's explanation is really logical, I can easily imagine from him. Basically, proving no superusers is to ensure that each player's win rate is the same. In other words, it is a way to ensure fairness for everyone on their platform.
All I wanted to know basically is that if there is any technical way to prevent the possibility of superusers or we have no option other than trusting these poker platforms, (which can be very risky).
We can choose to trust or not trust a platform, we are free to decide, once we trust it, we have to take risks, of course, this risk is the same for each other to play on the same platform. Players on one platform cannot play against players on another, so their risk ratio is the same. A platform will never public any of their strategies in terms of security, so don't expect anything there,
Lakai01 has a great example for it.