This needs to be higher up. It's not just about color interpolation - this is a problem with nonlinear color spaces. If you interpolate in a proper linear colorspace, you still get a desaturated color in the middle, but it's the proper brightness and it looks a lot better.

Gamma correction is the bane of computer graphics, and in 2022 there is absolutely no excuse for not using linear colorspaces for all image processing. We have the RAM. 8-bit non-linear colorspaces are a compression technique and should be only used for file formats, not image processing, ever. So many things would look much better and correct if we stopped trying to incorrectly process images in a compressed representation without uncompressing them first.

For comparison: nobody has used A-law or mu-law audio compression ever since digital POTS lines, and we certainly don't process audio in that form, ever. It's the same exact concept as storing pixel values in 8-bits with a gamma function. But somehow we think we can get away with processing images in that domain. I guess it's because if you try to do that with audio, the result is obviously wrong to any human ear, while if you try to do it with images it only looks somewhat wrong, not completely wrong...