So, consequently, it would be silly today improve the quality of the swords by using better quality iron ore and modern technology? If yes, you are saying i.e. all modern American sword smiths miss the point even if their product have much practical better quality?
I'm not even sure where I'd begin on the topic. And lord knows I've got a lot of experience both with the old craft as well as modern smiths.
I thought Ellis' point was well made. There is some room for discussion, but that said, it is about learning to use that particular weapon. And it can become a remarkably complex, subtle and nuanced discussion (something rarely seen on-line) defining what it is that makes something 'authentic' or like the 'real' thing. All that said it even gets complicated at best when you talk about something even as ostensibly simple as material performance. Traditionally made swords had their properties including their limitations. And as such the swordsmanship practiced by many groups included an understanding of those limitations in the training. One avoids hitting heavy, hard targets instead targeting soft, more easily cut. One has to be careful on thick targets to get hasuji correct or else risk a bent or broken blade. Thrusts have specific targets and methods as the very tip of the sword is one of the most brittle parts. Heck, even proper drawing and resheathing can encapsulate some understanding of what is fragile and what is not (don't rack the sword in to the saya and don't whack the tsuka on too hard as that can cause deformation of the habaki making the sword loose, etc.).
I thought his point was well taken. It is complex. It is complicated. Then add in that some smiths today are making gigantic blades that are incredibly thin and very wide. Basically lawnmower blades with handles. And modern metallurgy can make those remarkably durable. And they do cut, boy, do they ever cut. But is it still the same weapon? Are you learning the same art?
Lots of questions and no easy answers I've ever seen over the years putting swords together for martial artists and collectors. Everything from incredibly valuable antiques to junkers from 400 years go to modern pieces.
I could ramble on for days on the topic... But regardless, fwiw, I agree with what I read his point to be on this. And I'll add that this same discussion has probably gone on for centuries whenever "advances" were made in the materials and/or when some old things went out of style. Why do you train? Is it effective "in the street"? The same question likely was asked about "dirt street effectiveness (tm)" kata designed for wearing of armor when the person in question happens to be living in 18th century Japan and no one is wearing that armor anymore. "Hey, sensei, why do we train in this is no one is wearing it anymore? It isn't effective in the street. And why are our swords so heavy when no one is wearing armor anymore?"