Reading those articles suggests that the term "elasticity" is being used wrong. Every time it gets used they seem to be referring to tensile strength, and in the case of the National Geographic article they outright quote a scientist using the term "tensile strength" then paraphrase with the term "elasticity".

This leaves a situation where the armor is going to do jack-all against knives, and where while it is less likely to break upon getting shot it still needs some rigidity to deal with bullets. There's also a distinct lack of mention of high caliber rounds, probably because it's still pretty useless for that.