Umm, do you know the basics of networking? Even if Amazon had the most amazing WAF that specifically looked for telnet vs. curl or code, they'd have to let them connect first on the standard port to start talking. Until a program starts talking specific protocols and going, the WAF is going to have to let them start.
Having telnet (or nc, or anything else in the world that can make a network TCP connection) all operates the same at the most basic levels of connecting out to a remote server on a specific port.
