I don't think that's quite right. The round rectangles are still perfectly round. But in the example given, the outline becomes fainter on the rounded section

I don't think that's quite right. The round rectangles are still perfectly round. But in the example given, the outline becomes fainter on the rounded sections, because gamma isn't taken into account. In other words, the shape is perfectly correct, but the antialiasing is buggy. (It also has nothing to do with gradient striping -- that's an unavoidable artifact of 24 bit color that has nothing to do with gamma. It becomes more noticeable if you don't dither, which generally isn't done in 24 bit color, or when compression is bad, like low-quality JPEG.)