Any communication we do with paypal uses CURL. CURL should use the latest version of HTTP and TLS, unless specified otherwise.
The curl tests you have done should confirm that your server has the latest http and tls version necessary.
Not finding any instances of CURLOPT_HTTP_VERSION or CURLOPT_SSLVERSION confirms that you haven't specified another version, so it seems you have verified that this is not an issue on your server. The letters are the confusing part, but I guess the only way to know is to wait for the date.