Scrubbing material roughness value in MI causes large frame drops

Open any project and turn on an FPS counter (NVidia overlay used for test)

Create a new material with a single scalar constant plugged into the roughness output node.

Convert the constant to a parameter and give it an appropriate name (e.g. RoughnessIn)

Create a material instance from the material and apply it to any surface

Open the material instance, enable the RoughnessIn parameter, and scrub the value left and right using the mouse (i.e use the mouse to increase and decrease the roughness value)

the frame rate will drop significantly, below 10 fps best case scenario, and the scrub method becomes unusable.