Sometimes, I see apologies stated with similar IP address or matching patterns, which means the sybil check algorithm might be relying on patterns that feels two things are connected because they have similar patterns or have similarities hence it flags them as one or cheater, this is one of the reason why don't use several casino because they could even scam you with such alligation, especially when there is an insane amount of win or huge deposit in your casino wallet/account. I also agree that because they are aware of this vulnerability of their checkers they leave the window open for those who will not find it likely to let go.
I do not know how this sybil check algorithm works at the backend but usually the casino should not flag the account using a similar IP address. There can be a reason that more than one people in a house share the same IP and hence we cannot conclude that using IP necessary means a same person. Also think of a situation where few people in the office using the same IP and accessing Spinly. You should not link all those account to a single person.
Apart from the gambling patterns, they should also look for the devices and mac addresses. Usually people who share IP addresses don't share the devices and hence there need to be through checking before concluding anything.