This is not completely unusual. Maybe they had collected many environmental samples for a project that had not yet been published and decided to release that i

This is not completely unusual. Maybe they had collected many environmental samples for a project that had not yet been published and decided to release that information to the public because it was a closer relative to COVID19. I personally have sequence data that I'm sitting on prior to publication that was collected 2 years ago and some others that are from around 6 years ago. It isn't completely unusual.