This isn't a sub-race in the same sense that 3.5 or earlier elven sub-races existed. They are mechanically identical to elves, and are only distinguished after the player decides to pick up a specific feat.
The mechanics were never the issue with the elven or dwarven sub-races.
The problem was when there were eleven different types of elves. "So, what's an elf - " "DUSK elf. I'm very different from other elves!" "And I'm a WILD elf. GOD." "Not Corellion." "What?" "God. Better not be Corellion. We dusk elves hate Corellion!"
I'm sorry, having stupid amounts of sub races is dumb. 4e doesn't get a free pass because it does it differently. It's still ramping up the sub-races, something they openly stated that wouldn't do.