It is not double elimination, if you lose a match you have one opportunity to buy back into the tournament. With DCC, it is not a standard tournament chart, they actually redraw after every round.
The original intention of the buy back option was to get amateur players to participate in the DCC. Amateurs could enter a tournament for a low entry fee. This would tend to increase the number of players in the tournament. One year at the Derby we had 476 players in the Bank Pool tournament. So, by and large this format succeeded in increasing the number of players in each tournament. The money from the buybacks goes towards the Master of the Table prize.