Why Indie Gala not and Introversion Bundle yes?

When you submit a Humble Bundle, it is only acceptable to have an unactivated gift URL to provide to the winner.

... oh maybe because the indie gala continues to operate and the Introversion Bundle already finished ?
that could be a good reason
if you could giveaway the active bundles this would be a chaos

Indie Gala goes in YOUR email.

Introversion Bundle is allowed because the period for purchasing it is now over

Gala have not giftable option, thats why.

If you really really really want to give the extras away, just find some other forum or chat and post them there. Problem solved, no more bundle complaints.