i’m not sure if the aspect binding thing really applies? theyre looking at it in terms of already knowing the 12 trolls and what they’re doing and using them as the default- but this stuff exists before they did. like as an example, ‘taurpio’ isn’t a combination of taurus and scorpio- it’s a combination of ‘taur’, the prefix for brown bloods, and ‘pio’, the suffix for prospit/light. there being a concept of a ‘true taurus’ only applies in terms of the human zodiac and using the 12 as an example.

 I’m…not sure I follow? The concept of a true Taurus applies because the Extended Zodiac refers to the sign as…True Taurus. Same for every other zodiac sign. And that sign is a Breath sign, in the zodiac itself. The coding is already in the extended zodiac system.

The prefix for brown bloods is Taur BECAUSE it’s derived from Taurus. Sure, that might not be literally true in the lore of the world, but it’s transparently true from our perspective. 
And Alternia–including it’s Caste system–were still predominantly set up by Lord English and Doc Scratch, who were/are predominantly exposed to trolls…through their memories of/being literally some of the trolls from Homestuck. The 24 trolls that play Sburb have always been an influence on how Alternia developed, to some extent, through the vector of LE.
So I don’t really see when they literally showed up to exist there as relevant to how this sociological structure is set up.