The casino never reveals the criteria it uses to detect multiple accounts. Some people think changing the internet connection or using a VPN will make them undetectable. A casino can use different ways to detect multiple accounts. It could be wallet reuse, IP address, same device, or even the same browser. There might be other ways that they use to detect multiple accounts, and the gambler do not have any idea about it.
When people think they will be able to dodge the casino, they are fooling themself. They will eventually get caught and later blame the casino. All we can say is sorry to them for getting their account banned.
Even though you are correct to a very great extent yet sometimes it might occur that the casino is mistaking somewhere, because I have seen and accusation somewhere not this forum where a casino apologised to a user for accusing him of having multiple accounts however it was all a misinterpretation of information from the casino server, so I can still say that not even the casino is immune to mistakes. However not also understand estimating the fact that people become greedy sometimes to go against the terms of services of a casino.