Yep, I recently got Google's Titan pair of keys, and anywhere that supports hardware keys, I was able to register both, and I'm only required to use one to login.
A surprising amount of Kickstarters are already funded, or at least, partly funded before starting their crowdfunding. I know of one case first hand that had secured X amount of funding based on the ability to secure Y amount of crowdfunding. So, very possibly that's the case here. Some investors see it as a way to prove there's at least some market for the product.