smoothness parameter slider problem

Hello All,

In the unity manual in Metallic mode: Metallic Parameter in Metallic parameter paragraph i read the following:

"With a texture assigned to the Metallic parameter, both the Metallic and Smoothness sliders will disappear. Instead, the Metallic levels for the material are controlled by the values in the Red channel of the texture, and the Smoothness levels for the material are controlled by the Alpha channel of the texture. "

"The problem is when i assigned a texture map the slider for the smoothness parameter still exist and i cannot control the smoothness value through alpha channel as it wrote in the manual.

is there any problem with my unity editor?

Thanks in advance!