imo the key thing about quadrants supposedly making more sense to adult trolls is that from a design perspective the entire point of the quadrants is to fuel teen drama, in much the same way sburb's themes of adulthood and reproduction are engineered precisely to have the greatest effect a cast of confused teens. as Homestuck moves forward from Act to Act it starts to heap more and more elements of interpersonal drama on top of the action adventure - which it makes explicitly clear is deliberate using gags like Spades Slick getting sick and tired of watching kids kiss on his viewscreen - and giving the trolls not just one but four unique different ways of being confused about their feelings was a calculated move to kick those teen feelings into overdrive. all of which is to say the reason the comic doesn't spend any time really exploring how adult relationships work among trolls is because Homestuck doesn't find emotionally mature and healthy relationships to be all that interesting and makes pains to avoids them like cooties