Good comment, I think patina have important role As well.I think that’s where the confusion lies. The Plasmas with its shiny finish changes depending on the lighting can look different, but that bronze tint that you mentioned with your Plasma under certain lighting conditions can be found. You won’t find to my knowledge that bronze tint that appears sometimes on the Plasmas with any of the 2 Titanium finishes.
You can’t compare BNiB frame from 20+ years with other plasma frame which is use often. The sweat, UV, time, care, maintenance, location, weather, and more Factors.