I entirely agree! I think the "kitchen sink" approach is vital - unless you plan to put in decades of work and hope that you end up with a Glorantha or a Middle Earth! And I think an important point is that a fantasy gaming
world should have many more species than a literary
one: tabletop variety trumps convincing ecosystems and the like!
My point is really that while the "meta-game" background for the hobgoblins is very clear, it would be nice to have a (brief) "in-universe" explanation linking the terms. As I see it, the "meta-game" genesis is something like this:
Tolkien's hobgoblins/Uruk-hai (a bigger, fiercer sort of goblin) > D&D hobgoblins (a bigger, fiercer sort of goblin - now sometimes orange and with an eastern look) > Warhammer hobgoblins (a bigger, fiercer sort of goblin - also sometimes orange, and with the eastern look specifically a steppe-nomad one) > Norindaal hobgoblins (orange and "eastern"/steppe nomad, like their gaming forebears, but without the connection to goblins that's always been part of the core concept).
So I think it would be good to have some nod to that in the game - something like this: "Dwarves and humans generally call the Hurras "hobgoblins", a disparaging term suggesting kinship with the Gobelar. But although the two races have certain physical similarities, there is in fact no connection between the proud nomads of the plains and the scuttling goblin-folk of the [wherever goblins live]."
It may well be that no one else thinks this of any consequence, though!