"NiceBot" is just a label, a shorthand way to refer to those 15 strategies (which notably were the only 15 survivors in the evolutionary tournament). I agree that it's not a very precise name. Another way to identify them is that they're the strategies that never defected first, outside the endgame. Your strategy was designed to defect first, in an attempt to exploit overly-cooperative strategies. Perhaps we could call the 15 the non-exploitative bots (although that's not perfect either, since some bots like P and Z defect first in ways that aren't really attempts to exploit their opponent).