I am not sure if this feature is implemented. I see this here in this post that you can condition your file. But the help center article didn’t say anything about encrypted password protected imports generated by the Bitwarden export vault tool. The example JSON file given is an unencrypted one. To be clear, I am not talking about the JSON encrypted version associated with your generated symmetric key.
You can’t condition a password-protected .json export, because in that file format, the entire vault is stored as one big encrypted blob.