other possibilities of being accused of multi accounting are, using a VPN, using someone's device, using someone's internet, using a public wifi, using computers in an internet cafe, transacting with a wallet address that belongs to another gambler in the casino, etc...
The things I mentioned are the ones I've seen posted on the scam accusation board over the years as possible reasons for being accused of multi-accounting.
There should be no problem with using a vpn if you use it correctly. Of course, if a user uses a public VPN, there is a good chance that someone else has already used that VPN to access the casino. In such a case, there may indeed be problems because the gambling platform may interpret it as multiple accounts. But it's worth noting that not all casinos can react so sharply to the VPN. Some treat it more or less loyally.