glossiness channel supposed to be the opposite of roughness channel

HI

I'm compairing PBR specular workflow with PBR metallic workflow and specificly the roughness /glossiness.

They supposed to be the opposite / negative of each other. But when I use for instance 'Metal Polished' from Asset, the glossiness is a light gray surface without any structure in PBR specular shader setting. In PBR metal shader setting the roughness channel is darker grey but with structure. So not the negative of each other. Can anyone explain please?

thanks

René