At the moment, light probes in Eevee have a form of aliasing that makes rough surfaces look speckled/shiny. This patch mostly eliminates it by increasing the LOD bias as the mipmap level gets higher. It also increases the sample count a bit on the glossier mipmaps, which makes them look less blocky.

The difference is easy to see by going into LookDev, picking the studio HDRI and creating a metallic sphere:

It also increases the default Filter Quality to 3.0, which I think is the lowest setting where the reflections look relatively smooth.