(Gaary, watch out! Next thing you'll ponder is a stone tablet and chisel for data longevity!)
It might be helpful to remember that a BluRay's laser is incredibly more precise (smaller wavelength) than a DVD's which is many more times precise than a CD's laser. These wavelengths are smaller, finer, more precise so they can etch their version of bits & bytes into smaller physical spacings, too.
A scratch is a scratch.
But the fineness (the much higher precision requirements for reading and burning) make scratches probably exponentially impactful (not just simple multipliers).
The discussions of waxes and cleaners is amazing because I'd be skeptical of any add-on layering that wasn't exactly the same molecular alignment and composition of the original plastic layer. I'd think "light diffusion" would be too scattered with added on layers like a cleaner or 'scratch filler' might present.
Well... maybe my tests with guacamole and peanut butter weren't the best proving grounds for my theories. Perhaps... probably...
"What about TWO African swallows - ?"