5. To prevent abuse and ensure a fair gaming environment, users must complete KYC (Know Your Customer) verification before participating.
No. KYC is not mandatory but just like other casino, they may ask you randomly. The promotion that you mention is their way to attract new user to undergo KYC just to get the bonus reward.
I still have my account not verified until now but I rarely play on this casino these days so maybe this is the reason why my account is still not ask to KYC even if my account age is old enough.
"must complete KYC" doesn't sound like it's optional. If it only refers to the promotion, giving personal information and passing KYC is too much for a $20 bonus. I understand that it is a question of protection against multi-accounting, but there would have to be some other way to make it happen.
They are not making you do it, they are not going to offer people hundreds of dollars to do something that they have a rule that states they could ask for it as well. This casino doesn't make it mandatory for regular situations, but "may" ask if there is something, I assume if you win big for example, but if they have the right to ask for something then giving 20 bucks for it even though they can get it for free is still a lot.
This means that they are not really giving 20 dollars just to take your KYC, they can take it anyway they want, or worst case they will make you leave if you do not give it, so this 20 dollars has nothing to do with your KYC, it's just a promotion that has a requirement like that, it's that simple.