Did you not get the part where it's a last-hit lv50 boss drop? And that the crafted sword had attribute/stats that were even greater than the Elucidator? At segments of 25, 50, 70, 100, the bosses are freakishly, abnormally powerful. I think it says something about the raw OPness of his dual blades when he bursts down the majority of a lv74 boss's HP with...15 hits from a sword skill.

Yes, it's a combo item that can be wielded only by the person with the Unique Skill Holy Sword. But Kirito also has a Unique Skill, and even then, that doesn't mean Heathcliff gets system-guidance due to said skill, nor did he ever appear to use any sword skills related to Holy Sword.

(fuck, this is what happens when I start SAO raging)