When you fund a Kickstarter project, you're investing in the project.

If it does not fully fund, you receive a refund from Kickstarter.

If it does, your funds go to the project, who are on their best effort to successfully launch the project.

You are NOT, however, directly purchasing a reward. You receive a reward as a gift for helping to fund at a given level.

The teeth backing up that TOS is that if you violate it, you'll probably find it hard to get a new kickstarter project accepted. But that doesn't mean there's a legal obligation to fulfill rewards.