I think they're referring to using servo speed to control an entire large movement. Say from foot on the ground to foot up in the air with no interpolation.

My code runs at 50hz and calculates the position IK at every frame. It does use the default servo move speed though. In order for perfectly smooth motion those, the servo speed should change depending on the distance traveled for the set frame rate. I believe default is full speed, which may be too fast for a short distance and might introduce some jitter since it may arrive too soon and have to wait. It probably overshoots its position a bit as well.

I'm picturing real-time position and velocity IK at 30-50hz. The servos should move to the correct position at the correct speed for every frame. Ideally that would be pretty smooth