Gamma correct

It's not just you, but I don't think it's a gamma problem. It's known as "Mach bands", and it's a problem with how one perceives the images, not with the actual rendering.

There's certainly some Mach banding in these images. But that's not really the main visual problem here. The problem is that the images are not correctly tone mapped, even though they clearly use a bright HDR component in the specular highlight. The dynamic range is brought down with a simple linear clamp, which creates the typical halos of cyan gradients around the bright white highlight. This limitation comes from how colours are interpolated in RGB space rather than using the SPD (spectral power distribution) of the reflected light. The effect can be significantly reduced by tone mapping the image with an exponential exposure operator.

I see. Thanks for confirming my suspicions.