I noticed a general trend in 4e development to make everything (races, lore, mechanics) fit into the 4e established mould rather than make new things appropriate to the setting. It's how we got Astral Spelljammer (the astral being more central to the new cosmology), Dragonborn replacing every draconic race in every setting... and how we got primordial-tied Darksun backstory etc.
The end result was 4e wearing a Darksun costume rather than a 4e version of existing Darksun vibe/setting