This is not about PFS for transmitted data, only for client identity. Unless I'm missing something, an attacker will not be able to decrypt past traffic if they

This is not about PFS for transmitted data, only for client identity. Unless I'm missing something, an attacker will not be able to decrypt past traffic if they manage to obtain the private key, but they will know the public key of whoever sent it. In most cases this is a non-issue, but it can matter of you're trying to hide your identity behind a VPN.