This information has just been added to the Nova FAQ. Sorry it took awhile, but the committee did have an interesting discussion about it. There was general consensus among the mentors that leaving the adventures to be the last completed requirement was a “best practice”.
Q: For the Wolf/Bear Alvarez Supernova, the requirement is to “Complete the adventure appropriate for your rank”, with both a Wolf and a Bear adventure. If a scout earns the appropriate Wolf adventure in their Wolf year, but doesn’t finish the rest of the requirements that year, can they finish the Supernova in their Bear year, using the already completed Wolf adventure? Or, since they would be finishing it as a Bear, do they need to earn the Bear adventure as well?
A: The Scout should complete the adventure designated for the rank during which they have done the vast majority of the work for the award, as determined by their Supernova mentor. Under no circumstances should Wolf and Bear adventures be mixed in a single Supernova award.