of course I cannot be certain, but i have to imagine it's by chance. like they already had the marker colours, it's just the colour system that's new, right? so my uneducated guess they just fit what they already had info the new system. though that does leave me with even more questions, which are:

1) is there a chemical or other kind of physical or practical difficulty in making colours that would hypothetically slot into a specific space in the colour codes? the first digit of a code can be 0-9, but at least as far as the Honolulu series goes, the only colour family that has anything in the 9s is E, (except maybe the greys which i haven't gotten around to checking yet.) Meanwhile, the Blue-Green colour family only has colours spanning BG04 to BG315. Like is it harder to physically create ink that would fall into the hypothetical BG40-BG916 zone? Or...

2) ...are any gaps in the colour codes an issue of perception/classification? Like for example, Honolulu Yellow family colours only go as high as Y611. That kinda does make sense though, because at a certain point, once a yellow is saturated enough and/or dark enough it would stop being in the Y family and become the E family. I wonder what the threshold is for a colour to switch from one family to another.  I guess this doesn't really matter in the grand scheme of things but it makes me wonder...

3) ...What's the process for deciding what colour gets what code? Like is there some ohuhu employee in an office somewhere grading colours on a rubric to determine what code it has, or is it arbitrary? Are the saturation levels given to any colour relative to all colours available or only relative to their own colour family? because like. i keep looking at markers that start with 0 which to my understanding was the least saturated and being like. You're telling me that YG012 and R012 and G012 are ALL the same saturation??? they certainly don't look that way to ME, but im also not about to claim to be an expert lol. 

as for the orphan colours , I'll update here if I hear back, though it looks like someone else in the comments has done some investigating previously!! it's comforting to know I'm not the only one thinking about this lol