This is not about the provably fair of a thing, as it could be proved to you now that it is provably fair but later adjust it, and even those provably fair we see are not as they claim because, which company will make their platform to be an open source for people to painstakingly and sincerely verify?
Just a small correction, a provably fair game hasn't to be open source as you suggested. All you need to know as player to verify the fairness of a game is how the outcome is determined and the variables used to determine this outcome.
Also, you can verify all the results at any time you want. So, it will be easy to know when the casino start manipulating the results.
Correct, that is a quite common misconception I have seen before,.specially from newbies who do not understand how seed verification and probably fairness works in the first place.
If we lived in a ideal world, all the software used by casinos and game providers would be open source and this could give undeniable access to the way those games work, though, that is not going to happen anytime soon. because it would be imply an oversaturation on the market by services which would be always the same thing one and over again.
that is why probably fairness was conceived for in the first place, so people can make sure they are not being ripped off by the casino, within the need to verify the source of it running on the background.
As mentioned, it is not only a system about using one's seed to generate the entropy to get a result, the fact cryptography also allows the gambler to verify the result and the seed are related is the true game changer when we talk about fair games and fair gambling .
It is a topic worth investing some time to read about.
I don't want us to build so much misconception about this issue around how fair is the probably fair games even the ones that have the games hash and could be verified using the block analytics tools, I have seen few casinos that prove to be fully verifiable and at the same time proven to have undergone some independent testing of their probably fair system, this made them bold enough in the entire cryptocurrency gambling market space with the claim of probability fairness of their game's.
I won't want to go into playing any doubt game whether or not those platforms are fair or just claiming to be fair but just on a neutral ground and supporting the whole discussion from my own point of view and long-term experience, I think development has gone pass when some casino will just claim what it is not, and we should know that those games verification to test the probable fairness of the games is selected games and, not all games can be verified.