you describe the holes in the disc as being for heat dissipation. Over here we've always taken it that they are to get rainwater off. Early Japanese discs were chrome plated for looks and had no holes, they were a disaster in rain -- about zero braking until the water dried out, then locked wheel!
It was strictly a SW
AG on my part. The water-removal concept makes sense; I hadn't really thought about it that way. My notion sprang from two thoughts—(1) drilling holes increases surface area somewhat, thus improving heat-transfer properties; and (2) gives a bit of benefit in weight-reduction without affecting braking power. (Indeed, Constellation's input makes me think it
improves braking.
Early Japanese discs were chrome plated for looks
Chrome-plated braking surfaces!!?? Were they waxed (or lacquered) as well??

Reminds me of something I saw, back when. In April 1970 when the the US Marine Third Amphibious Force (IIIMAF) relinquished operations in the northern part of RVN to the Army's XXIV Corps, the mentally-challenged US Army colonel who became the Headquarters Commandant of the former III MAF compound (Camp Horn, Da Nang, an old French Foreign Legion compound, BTW) decided to beautify the compound —
so he ordered that the interior-defense bunkers be painted white!!! Anyone have an idea what a firing slit in a white bunker looks like at night? You got it —
a bull's eye on a target (even with little or no moonlight)
This was the same guy who put white one-foot-high picket fences along the walkways in the compound. That was all we needed: punji stakes to injure people running in darkness for the bunkers during a night rocket attack!
I was in the Army at the time, working at IIIMAF in a US Air Force facility. Made me appreciate the Marines!