I think by client you mean the device and operating system, which is correct to my understanding, but it’s confusing because ‘client’ can also mean the VPN client software which is often supplied by the VPN provider, and that’s what I first think when you say client. So with that in mind it sounds like you’re saying “it’s not about the VPN but the VPN software” which obviously comes from the same provider.
I have not looked into it so you probably understand this more than I, but from the sound of it the VPN software can be built to detect, prevent or counteract the exploit even on affected systems? In which case, even though it’s an environment issue it can still be resolved by the VPN provider.