From what I understand by what Rhavar is trying to explain (which I will turn into layman terms for people who are like me that have hard time understanding technical talk) the game "looks" like it is fair but they do have a secret way of knowing if you are gambling by checking the seed or not.

If you are a guy who doesn't check the seed that often they hide the previous seed so that you can't get it and that means you can be scammed out of your money, that is only if you don't care about the seed and not checking anything which they can see by you not changing the seed frequently or maybe even never.

So, it does "look" fair and that is true but if you let them away with it by not checking they could potentially become not provably fair given the opportunity. This doesn't mean they are stealing money from you, it just mean they have that option if they want to and you have to trust them not to do it which is not provably fair if you ask me.