This is written by the KiTTY developer. My guess is that when you open up a kitty session, you're not trying to open a subsequent one inside. So running `kitty` inside a session will give you a preview of the new protocol being proposed here
Are you certain? This looks like it's written by the author of the newer kitty terminal emulator, not the older KiTTY ssh/telnet client derived from PuTTY.