I read this entire thread dating back years and I didn't come across anyone who took out their stock fuse and appropriately cleaned it with alcohol and a small gentle wire brush to remove any oxidation and then compare to X new audiophile fuse. I'm not saying fuses don't matter, IME they do, but to get a more apples to apples comparison one should ensure their old crusty fuses' contact are as close to new as possible..
Just about annually I clean metal contacts on my components. This includes pulling out the fuse and cleaning the holder and fuse. After putting things back in place I’ve heard subtle improvements, but nowhere close to the magnitude of improvements I’ve heard from upgrading to a better fuse..
I see your point though about not cleaning the former fuse first just to arrive at closer to apples-to-apples, but had that ever impressed me as worthwhile I would have done so,