Anycubic I3 Mega Silent Extruder Lever

This lever stops the annoying loud "click" noise coming from the extruder unit.
(Just fit a short 4mm dia. PTFE teflon tube in the hole,
printing position should be same as the image shown above.)

Have you ever wondered where the clicking noise is coming from?
There's so many false claim about what makes the "click" noise, such as
...Extruder motor does not have enough torque.
...Extruder gear is slipping, etc.

But none of the above are the real reasons.
Here is the real cause:
The