As pointed out in the article, this is basically a direct consequence of the commercial crew program: "The contracts call for orders to take place prior to cer

As pointed out in the article, this is basically a direct consequence of the commercial crew program: "The contracts call for orders to take place prior to certification to support the lead time necessary for missions in late 2017, provided the contractors meet readiness conditions." There is plenty of time for NASA to back out if either of the companies don't meet the milestones.