This is likely due to how there is not a single manufacturer for this stepper motor, and thus a single model name covers both the 5V and 12V version, and a wide spectrum of gear ratios.

He used two 5V stepper motors with ULN2003 drivers. These motors are mounted on the back and rotate the knobs via pulleys. They are kind of slow; it takes about 2 1/2 minutes to draw the time ...