Question Changing URP Material Properties via Script will change the values, but not the actual material

I have a URP Simple Lit Material which uses Specular Highlights (enabled by default - so the Shader Variant stays the same throughout the process).
I want to change the Smoothness via Script.
This is the line of code:

Code (CSharp):

1. wood.sharedMaterial.SetFloat("_Smoothness", s.value); //s is a slider

This does work. When I use the slider I can see the Smoothness-Value of the material change accordingly in the inspector.
But the Material itself does not change at all - even with obvious changes from 0 to 1. The way it renders stays the same. Only after I touch the slider in the Editor / Inspector it will "apply" the values.
What am I missing? Do I need to call some sort of Apply Changes Functionality?