In my opinion, the issue of multi-accounts should be evaluated on a case-by-case basis.
If there are many accounts opened, linked to the same owner/device, and bonuses have been taken with these accounts, then it could be considered an action to "cheat" the casino. But if for example there is 1 account that spent a lot of money and played often, and then there is another empty account, which has never taken any bonuses, I do not think that the second account was opened to "cheat" the casino.
For example, I could have opened an account years ago with the casino, and I never used it (and I didn't use any bonus).
Some time later, I forgot I had an account with that casino, opened another account, deposited and completed the KYC.
In this case, I do not consider it an action to cheat the casino.
If the user is self-excluded, then opening a second account to play, violates the rules.
However, at least the option to refund deposits or the total balance can be considered