How is "mislabeling" cognitive distortion different from "labeling"?
It seems that in this case David Burns describes Labeling as an overgeneralization, not necessarily a misattribution. As in his example, a breather does breathe, it is just not the only aspect of the breather.

Mislabeling in this example is an inaccurate label, not an overgeneralization but qualitatively false, and "emotionally heavily loaded".

This explanation would fit with regular English semantics for the words, so it seems to make sense. I would not qualify the terms Labeling and Mislabeling as rigidly defined per this text though.