(starting with your point about Miyamoto); that is actually false . Not in the way you'd think though. See, while the techniques he employed were the same, he could not affect a killing slash with a Bokken. That is straight-up how you kill people with a Katana; his employment of the technique with the wooden sword failed ultimately because they cannot be effective in the same manner.
I wouldn't call it a failure, as it did in fact work. His first slash tripped Kojiro, and the second slash shattered Kojiro's ribs and punctured his lung, killing him. While it didn't cut him per se, the fact that it still crippled his limb and then dealt a deathblow suggests that you''re incorrect.
And, like the Khopesh, you're not going to cut through much if you've got an aluminum one. So while one part of it may be unaffected, that does not mean the entire thing is unaffected - much like my original point; these future-fantasy weapons are not the same as their real-life counter-parts.
True, it won't hold an edge. But the same strokes, motions, and defenses that work best with the aluminum one will still work best with the one made of carbon steel or super unoibtanium or whatever. Using the disarming hook to try and disarm an opponent is going to be the same regardless of the blade's composition.
Or are you suggesting that two identical blades of differing degrees of craftsmanship are not used in the same manner?
So to the first part of your response; his first slash tripped his opponent. Tripped . That is not a success.
His second attack shattered ribs. Shattered . Again, that is not a cut in any sense of the word; clubs shatter things. Blades are meant to cut things. That sounds like his techniques were not put to their maximum effect - two attacks that should both be deathblows were required. That is called a failure .
See, anyone with a club can bludgeon a man to death; the reality is that his technique had nothing to do with how clubs destroy a human body - via blunt-force trauma. That he could use a particular sword-fighting technique and not be totally ineffective though only speaks for the technique's particular range of weapon-adaptability.
I mean, consider if his technique had been that of a medival knight and his weapon was a longsword; he had better hope that his opponent was not wearing armour, because otherwise he would not have a hope of victory.
Basically, while some techniques may make use of some aspects of a weapon, they are designed for a specific weapon made of specific materials. That's how these techniques develop.