The attached image says “(see more with ‘–help’)”. And, in fact (I just tried it), the output of --help contains a lot more detail.

Edit: for more information, fd uses the command line argument parser library clap, which has both help and long_help properties for arguments, which are displayed for -h and --help, respectively.

Email isn’t “the only way” to send patches. In fact, he addresses that:

It doesn’t have to be by email, either. Any method of sending this data to the maintainer is fine. For example, I’m on Mastodon – so you could send me a repository URL via Mastodon if you really wanted to (provided you didn’t mind my responses being very short). Or you could send patches via any other communications medium that you and the maintainer are both on, if it lets you attach files to messages.

His preferred method is just sending a URL over email. You can use any communication method if you both already have an account.