Making large silicon boules is cheap enough that I'm sure what they plan to do is just square off the sides of the boule before sawing into wafers. The scrap from that process, since it is pure silicon, can just go back into the pot the boule was drawn from (it might need some cleaning steps first), so there is effectively no wasted silicon.
I would imagine, as it stands today, that packing rectangular chips into elliptical wafers has a certain amount of waste that can also be recycled. Actually, I suppose it would be less wasteful to fill the ellipse with rectangles up to the safe edge than it would to lop off entire sides of a boule to make a rectangle for filling.
I don’t mean to insinuate you are wrong - I need an education on how this rectangle business is better. Maybe they’re just trying to remove the “lop the sides off” step?
Packing rectangular chips onto circles has waste, but that waste cannot be recycled. It has been processed through a lot of different steps that contaminate it. I'm not sure if it gets recycled, but it's going to be a lot harder to recycle than large chunks of pure silicon.