Shadowshocks is not a VPN at all. It's a connectionless SOCKS5 proxy. No hand-check, no key exchange, no protocol agreement.
VPN is not made to be undetected, only secure in the sense of data encryption. Shodowsocks has broader objectives.
On your local workstation, it exposes itself as a SOCKS5 proxy. But to communicate with the shadowsocks server, it uses a proprietary protocol which is not SOCKS5 and does have a key exchange process. Either way, these details don't affect its ability to be detected.
> VPN is not made to be undetected
"VPN" is not just one technology. Many vendors of VPN software do claim that their software is made to be undetectable. One example is shadowsocks, but there are other vendors who also claim that.
Thanks for the info, couple of things I didn't know. What I meant by "it's not a VPN" was mainly it doesn't make your computer part of another private network.
See https://shadowsocks.org/ for info.