If I am not mistaken, in these cases it’s a duplicate. The left and right channels are identical (same track). I think that if it were 1.0 it should sound only from the center channel. Is there any advantage with 2 channels? Shouldn’t it always be 1.0?
2.0 tracks probably have better compatibility, for example my old Panasonic player outputs 1.0 PCM as 5.1 with only the center channel active, which works but is kind of weird.