This is the sort of thing they should have done at launch and then waited a while for any sales or bundles. Doing it after the fact seems pretty pointless.
I agree, the timing does not make sense to me. Nevertheless, it is a nice set.
I'd be tempted to ask what extras are included, but I doubt there's anything substantial. I keep going back to the time I completed the bonus scenario, which is triggered by finding all the eggs.
I may have been spoiled by Braid's star-fetching affair, which at least extended the ending by a whole 4 seconds. In LIMBO, the player is simply sent back to the main area upon the bonus scenario's completion. An "Achievement" was gained, but nothing of any true consequence came from that little trail-and-error-in-the-dark affair.
You made me sad, LIMBO, and not because of your story.