When the CC system detects K+N vs K+B however, it also automatically assigns a draw. No mating potential is given as the reason. However, this is *not* correct. It is possible to construct a mate rather easily, e.g. Ka6, Nb6 for white and Ka8, Bb8 for black. It doesn't matter if one side has to (willingly) cooperate to make the mate possible. Also endings like K+2N vs K, which are theoretically drawn, still have mating potential. It is possible to lose these positions.
Having seen this when watching a game I assume that other combinations exist where the CC system will incorrectly assign a draw.