How does Safari (on iOS) decide when to present an SSL client certificate
Safari (or any other web client) doesn't present its client certificate unless requested by the website. So your client certificate is safe. The server is always the one asking for the certificate, sending along its own certificate. Therefore, your browser will see that the certificate do not match the one you have and will result in failure, unless the server sends the right certificate to match yours, in this case, you can be sure you're on the good website.