I would say that it impossible to *know*, randomness and fairness are very often debated in maths universities and school playgrounds and it is a subject that is easily mis-understood (which is mostly why people gamble).
However, I have done a lot of gambling and poker over the years and the successful houses are the ones that are trusted - especially in on-line gambling.
That is why the more respected sites continue to plow so much resources into spotting cheating and robot players, because -in poker and other games of skill fairness is important, not so much with pure random games, where the honesty of the house about the odds is important.
The successful houses know that the easiest way to do this is to actually be fair, take your cut, be open about it, and you will still make a fortune.
As soon as a site is rumored to not be fair they shed players massively - even though such rumors are usually false - at least with the established providers, so it is just not worth it to cheat in providing gambling services - unless you are a very short-term scammer, who wants to make a quick buck and run. Which would be stupid as you will almost certainly make more money in the near to long term by being honest.

I don't know the provider of this site, but I have played it and I do like it.
Just responding to that particular question.
dM