There is a very thin line between the greed and the risk in this case. The reason is that if you do not take profits at certain key levels then it is highly likely possible that bitcoin may not move further and you miss out taking profit and holding your coins for another bear market.
Risk and greed are two different thing but they are related to each other. Risk accompany greed or any kind of investment. It is that the greedier the person is, the higher the risk he has to encounter. Like what you stated, instead of a person selling his stash at the current price, the person intend to have a higher percentage of profit thus greed triggers this kind of action. As this action is taken, risk arise from the possibility of the price of his stash plummeting and any other negative thing that may happen in the future.
I wouldn't call it a risk nor I will call it a greed but I will call it a sensible way of exiting at the top. No one can call the exact top, it's all speculations.
True I read from somewhere that this kind of situation triggered by greed probably called "
speculation frenzy" or
irrational exuberance