Unfortunately that doesn’t fix the real reason most people use VPNs, which is torrenting. Nobody should be using NordVPN to hide from a nation state, but for torrenting they add one level of obfuscation.
I think the reason why the method you mention isn't commonly used is that it is complicated to understand/set up and hard to verify.
I've seen more advanced users encapsulate everything in a VM so that non-VPN traffic can be blocked globally by the OS.