Bytemeister's anecdote related an example of his personal altruism. Which, I assure you, makes him the rare exception rather than the rule. Most people would not care or go out of their way to do that much or even think about it at all.
That does not contradict his statement that you cannot base a society entirely off of the expectation that everyone will always be that caring and altruistic to the point where we can all rely on and expect the altruism of others to always be able to meet our personal needs.
Bytemeister can simultaneously be altruistic himself, while acknowledging that the average member of society is not altruistic enough to make a system like that work for any length of time.