What is the parameter for the celeste pedal doing exactly?

There is a parameter for the celeste pedal which can be set from 0.00 to 1.00
At 0 the pedal being completely up and at 1 completely down.
What is exactly this parameter supposed to do?

If I remember well on a real upright there is a mechanism to block the celeste pedal down.
Is it indeed possible for a player with a real piano to use the celeste pedal smoothly between up and down?

Of course I hear the timbre difference but I would like to know which physical action this parameter is supposed to emulate.
The pressure of the felt on the strings as if the player would continuously press the pedal from up to down?
The thickness of the felt (someone mentions this on this forum)?
Something else?