“It also sends fake "chaff" keystrokes for a random interval after the last real keystroke.”
Encryption hides what you type in SSH, not when you type it. Damien Miller’s fix sends traffic every 20ms whether you type or not and pads the end with fake keystrokes. The first user complaint is a Netgear switch whose per-packet LEDs now blink nonstop. That blinking is the leak OpenSSH just plugged.