[....]is part of what we agreed when we sign up to play in casinos but lately I've been reading a lot of complaints about casinos on how they accept their players' KYC, is it possible that they can decline a person's credentials even though he swore that he submit all the right documents and even undergo a video call to establish his identity?
You cannot dismiss the fact that there are players that abuses casinos and tries whatever means necessary to get around their security checks such as KYC. They can fake their documents or even buy one on the black market. They can also pay someone to pretend as him during video calls.
Both parties the player and the casino can agree to do a mediation through third-party/parties. but do you think it has bad consequences if the third party proves the player is right in establishing his identity, then the casino's KYC is not reliable?
It may affect their reputation but that's part of the business. They have to improve their system so those mistakes don't happen again.
If the third-party proved that the casino is right but the player swore that he submit all the documents and is willing to do the extra mile to establish his identity, can we conclude that Casino's KYC procedure is different and we have the right to know how and what system they are using to decline our submission because we can be the next to suffer from this Casinos' KYC system?
Why still pin it on the casino when there is already a third party involved? Nothing wrong with their system as proven by the mediator.
You can ask but you have no right to just demand casinos to show how their security checks works when you're not even the player involved since it also poses risk on their part.