OpenVPN is an open source software based on client-server architecture and is definitely used by many VPN 'Providers'.Airvpn is openvpn
Also Avira phantom vpn is from openvpn so all the same
But you know what, it won't offer 100% privacy (and this is known) needed by the VPN providers (NordVPN, AirVPN, Avira Phantom VPN providers).
Each of them will tweak, add to and fortify provisions of the OpenVPN structure and then deliver their final product.
If all products using the same base were equals, then selecting the best distro (for security and privacy) among the many distros built on 'Ubuntu' for example, shouldn't matter because all use the same base ie. Ubuntu.
(Didn't give an example on different 'Linux' distros because many are built from scratch and have different bases to offer).
But it matters. Some distros built on Ubuntu itself, like Elementary OS, have some different provisions (mostly additions or tweaks) for security than stock Ubuntu.
So to answer in short, there will always be some differences in technicalities and offerings of the VPN providers using OpenVPN, by choice, limitations or needs.