No. It works in a very simple way. The visitor's IP address is pinged by the server running the test. At the same time, the client establishes a websocket connection to the server, exchanges a few messages, and latency is measured this way, too. The detector exploits the fact that most for-privacy VPNs have a NAT, and therefore the TCP/IP ping test would measure the latency to the VPN server, while the websocket test would measure the latency to the actual client device. A difference would thus indicate a VPN. In practice, this also triggers by a mobile connection while roaming.

Of course this does not work for VPN services like PureVPN, OVPN, and SwissVPN that provide a real public IP address to the client (so both pings measure the latency to the client), or for VPNs that properly firewalled the external NAT IP so that it is not pingable and does not send TCP RST or ICMP Port Unreachable messages when probed. But PureVPN IP ranges are known, so it is detected that way.