What we consider "maduro" is actually a combination of leaf and fermentation/heat. If I remember correctly it more defines that process than the color.
Most often thicker leaf (think broadleaf with DE or Nicaraguan with padron) that is sun grown and then heavily fermented to produce the thick, oily leaf that we refer to as "maduro".
Versus in Cuban a crop can be shade or sun grown, but the process of categorizing the leaf color while they roll (much like color matching wrappers in boxes) is done after the harvest with what was produced by the field. Like (you mentioned) how you have some boxes from other brands that sometimes come with darker wrappers and vary box to box (or code to code).\
JMTC
Great info.
I was aware that maduro refers to a process more than a color as i have seen the wrapper of some cc's listed as maduro, but the cigar was not referred to as a maduro in the name.
Perfect example is some QDO 50's I currently have with very dark wrappers i would call maduro by color, but obviously are not called maduros.
In fact, I'm fairly sure in the cigars I reviewed here in collaboration with Roger, there were likely some i listed the wrapper color as maduro, but they were not named as or "true" maduros.
So many little nuggets of info about cigars that you never stop learning new things...
I friggin' LOVE cigars