They are setting that time limit so existing users can't call to return Oculus saying "I don't agree to these terms" because _they aren't terms yet_ for that user. But by the time they finally require you to log in with the account, it will be impossible to refund because you are outside the legal warranty period for both US and EU.

It's planned exactly to trap people who already bought so that some percentage will "give in" and just log into Facebook so that they don't suddenly have a VR device (and VR library) that's not worth anything to them anymore.

There are far more people who will do this than those that won't, and that's a portion that COULD have returned it if Facebook was allowing them to.