Why is the "No False Lemmas" approach an inadequate repair to the JTB account of knowledge?

It has been shown that replacing the justification condition in the classical account of knowledge is neither necessary, nor sufficient, to grant a person knowledge. 

Consider a person driving through 'Barn Facade country', when he happens to see the only real barn in the vicinity and forms the true belief that there is a barn in the field. Clearly this passes the 'No False Lemma' approach, but this "knowledge" was obtained in an entirely lucky fashion, so one would be relcutant to truly grant this person knowledge; thus the approach is not sufficient to guarentee knowledge.

Similarly, imagine a person who sees a large crowd from a distance and is told by an onlooker "there a 80 people in that crowd", and consequently the person forms the true belief that there are more than 5 people in the crowd. However, it turns out there is only 79 people in the crowd - the onlooker was mistaken. Here, we would certainly want to grant the person knowledge but 'No False Lemmas' denies this. Hence it is also not necessary for knowledge.