I do disagree that a work would be ineligible if the publisher didn't make sure the books came out in the same calendar year. According to the rules, "3.2.6: Works appearing in a series are eligible as individual works, but the series as a whole is not eligible. However, a work appearing in a number of parts shall be eligible for the year of the final part." This leaves room for either your or my interpretation of whether or not Blackout/All Clear should have been eligible (is it a series or a work in parts?) but it does clear up what happens if the publisher doesn't make sure they come out in the same year.
Re: About treating them as one book
According to the rules, "3.2.6: Works appearing in a series are eligible as individual works, but the series as a whole is not eligible. However, a work appearing in a number of parts shall be eligible for the year of the final part."
This leaves room for either your or my interpretation of whether or not Blackout/All Clear should have been eligible (is it a series or a work in parts?) but it does clear up what happens if the publisher doesn't make sure they come out in the same year.