Wasn’t the use of Blu Ray footages to build correct HD versions of the OT a stopgap until we have good original sources ?
I thought it was just because the Blu-ray is still the best version available despite its flaws? And looking at that comparison you posted… well it’s quite close, but the BD is still noticably clearer, so from where I’m standing it still makes sense to use the BD-footage where possible. Though with the film prints looking like that, we are at a point where it can be pretty seamlessly combined with the BDs I suppose.