Change radius and size values (QOL) – GIMP

Why are the values for brush sizes different in the ‘tool options’ tab and the ‘brush editor’ tab: in both tool options and brush editor the size of brushes can be adjusted with sliders, in tool options its by ‘size’, while in brush editor its by ‘radius.’ When I adjust the ‘radius’ slider and reset the brush size in tool options their numeric values are different and when I look at the max values in both sliders they are also different.

If these two sliders both change brush size, then why aren’t their sliders use the same magnitudes?