Perhaps it was a different optimisation, but it definitely made significantly downscaled PNGs look way worse under particular circumstances. It was especially noticeable on triangles we used on nodes of a tree view control.
Yeah, images with sharp contrasts like line art tend to do badly with the scaling algorithms that work well with photos. It is why browsers introduced `image-rendering: pixelated` css, but as you noted in the other comment, SVG is almost always the best answer.