[scythe]

Steel, itself, is a material with a wide range of properties. In terms of tensile strength, which is the simplest kind of strength to measure, steel ranges from mild steel at 400 N/mm^2 to piano wire alloys at about 2500 N/mm^2. "Stronger than steel" is a flashy appellation that usually means you have just reached the bottom end.

A similar phenomenon occurs sometimes in papers about ceramics research. A very tough ceramic will often see a comparison of its fracture toughness to that of aluminium; as you've guessed, this usually refers to the toughness of pure unalloyed aluminium.