This is just the supervisor asking them for further information on cashing out, probably because that ID hit something in their database.
You are probably right in suspecting that we were not shown everything in the video. Perhaps the author of this video is trying to show the current situation from his side (to present himself as a victim of the casino's tyranny).
I doubt that the casino would delay (cancel) the payment of the $25k prize without reason. They have millions in turnover and it would be very reckless to risk their reputation for such an insignificant amount of money for the casino.
Comparing these two factors, I am inclined to believe that the author of the video is hiding/not telling something.
I didn't even think of it that way. But after reading your post, I was like what if the gambler is the cause why the casino are refusing to pay him. Maybe they asked him to provide something probably an ID and he couldn't provide it. In his effort to getting his money he is now trying to blackmail the casino by creating attention and the video was made and people are just believing that the casino refused to pay him. I went and rewatch the video after reading your post and it was then I understand what you were talking about.