I don't even know if brighter is the right word... Maybe crystal clear, maybe even thinner in someone elses opinion.

Maybe thinner is the word. I don't know enough about tuning reeds to presume, but my favorite builder has written about tuning reeds, but never ever specified how he does it "by ear" to me.

Perhaps the reeds in my favoritve accordions have been scraped "thin" enough to sound brighter?

I don't know how it's done, but I know I've heard Bincis sound different in different brands. In fact, VERY different.