Pre-ordered bike might be delivered earlier than backers bike, it is even possible that the bike are commercially available before a delivery to backers.

In such a delayed project with unexpected additional costs, the most important is to collect money on top of the funding by the backers, pre-orders are the first possibility, selling commercial bikes is the second. So, producing bikes for the pre-orders and for new customers has an higher priority than producing bikes for the backers.

Such a process already happened in other kickstarter projects.