If you are showing a gradient, then the colour-blind people of the world will tell you in quite strong terms not to use a rainbow for the scale at all, let alon

If you are showing a gradient, then the colour-blind people of the world will tell you in quite strong terms not to use a rainbow for the scale at all, let alone to use a rainbow that has been designed to have this sort of perceived lightness curve. The headlined article is a rainbow, not some universally applicable colour scheme.