You're forgetting that "strength" has a formalized engineering definition, which is the amout of force (not energy or impact) a material can resist before deforming or breaking.

The other 2 properties you're alluding to are hardness (force needed per unit of deformation) and toughness (energy absorbed before deforming or breaking. All of these are important factors when choosing materials for a particular use case.

The article is comparing the material to kevlar and spider silk, which suggests that they're referring to tensile strength, which is a proper use case. It isn't the paper's fault that your are incorrectly conflating "strongest" with "best". What's best for any particular use case is going to be dependent on design requirements.