This is not true, you can use VPN, but you can't have multiple accounts just by using different VPNs.
Freebitco is blocked in some countries including my country, so some members like me are forced to use VPN. I'm using this site since a decade ago and had no problem at all.

I can't speak for why other casinos do what they do but we don't block VPNs because lots of gamblers value their privacy. Using a VPN to gamble shouldn't be any reason to get flagged.