Thats not how SAR's are meant to be done. There has to be at least suspicion or belief that a breach of the money laundering laws is about to take place
If a person knows or suspects that he or she is about to deal with criminal property (in other words if that person believes that he or she is about to commit one of the principal money laundering offences under sections 327, 328 or 329 of POCA) then it may be a defence to such an offence if that person makes an ’authorised disclosure’ and, if the authorised disclosure is made before the transaction takes place, that he or she has the ’appropriate consent’ to conduct it.
and
3.15 The statutory mechanism under POCA, which allows the NCA to grant permission for a ’prohibited act’ by an operator to go ahead where the operator deals with criminal property, is known as ’appropriate consent’ 18 and may provide the operator with a defence against prosecution for committing a prohibited act. As noted above, where an operator fails to obtain appropriate consent from the NCA, the operator or its employees may be committing a money laundering offence. In order to obtain the appropriate consent, the operator must make an authorised disclosure to the NCA.
3.16 The decision by an operator whether to obtain appropriate consent will arise where the operator believes that, by proceeding with a customer transaction, they will be concealing, disguising, converting, transferring or removing criminal property; facilitating the acquisition, retention, use or control of criminal property by, or on behalf of, another person; or acquiring, using or possessing criminal property.
The casino either thinks or doesn't think an offence is about to take place. Refusing to supply documents should not influence that belief, unless of course the customer states something along the lines of 'I'm not supplying that, I make my money by selling drugs', then it would be grounds to submit a SAR.
They shouldn't even be doing AML checks to this degree unless the customer is deemed high risk.
18.6 In order to detect customer activity that may be suspicious, it is necessary to monitor all transactions or activity. The monitoring of customer activity should be carried out using a risk-based approach. Higher risk customers should be subjected to a frequency and depth of scrutiny greater than may be appropriate for lower risk customers. Operators should be aware that the level of risk attributed to customers may not correspond to their commercial value to the business.
18.7 Where a customer is assessed as presenting a higher risk, additional information in respect of that customer should be collected. This will help the operator judge whether the higher risk that the customer is perceived to present is likely to materialise, and provide grounds for proportionate and recorded decisions. Such additional information should include an understanding of where the customer’s funds and wealth have come from. The need to 'know your customer' (KYC) is particularly relevant here. While the Commission recognises that some relationships with customers will be transient or temporary in nature, operators still need to give consideration to this issue in relation to all customers.