Likewise, $450 HN offer received - but the Travel credit was recently used.
I suspect that perhaps the offer was targeted for all those with unused Travel credits due to expire during the period, but there is a bit of a timing issue in what they have done.
1. Some weeks ago, trawled through and found all the unused Travel credits for the period, and made the list of who would be eligible.
2. Worked out how much they may potentially be up for, and negotiated with the various affiliates (Qantas, HN) - factoring in who may not use the offer etc.
3. Finalised who got what offer - can't see much obvious correlation, as there seems to be a wide mix reported.
4. Loaded offers to cards
5. Ran another job to remove all unexpired Travel Credits for the period (probably not using he list from point 1, but even if it did, no doubt accepting that some would not be able to be removed because they had been redeemed).
6. Sent emails.
If you managed to redeem your Travel Credit in the time between points 1 and 5, you are effectively getting a double dip. Win!