You seem to like throwing unfounded accusations around? CM members are giving their thoughts on the situation based on your information, the casino will similarly have their own information that we are not party to.
There are lots of things that will get an account flagged - in crypto I would expect links to known bad wallets are the leading concern. For them to be asking for six months of transactions is clearly excessive, so either there is a genuine concern on their part or it's a blatant stalling tactic - something that could be clarified
during a PAB.
The reason "webcam selfie and id" often isn't enough is because the fraudsters will similarly do that by default (anyone who watches scambaiter videos will see frequent photos retrieved from scammers of elderly people holding up their ID) - so they can send images taken days, weeks, or even months ago as "proof" the fraudster is the person in question (which of course they are not).
As said before, as long as the liveness tests are reasonable (photo at the nearest road sign, 1 minute video call, app-based video verification) then that shouldn't be a problem - and it's a variation of the selfie with id of old but with stronger security (because it's harder to fake real-time video currently, or harder to fake randomised requests - but not foolproof though because scammers can coerce victims into doing it on their behalf).