That’s not true. There’s an infinite numer of ways to route IP addresses on the internet in fact. Most of them are useless however.
your VPN server can try spoofing its outbound traffic to use the client’s IP, but it’ll most likely get discarded by the ISP because it only allows your IP to go out. But even if you can, the answer to those packets will go to the client’s IP, which will go directly to the client and not the VPN.
Mission accomplished? This may be what OP wants? Really not sure.