Great points Ely. I note too that you added more about this in the What is a collection? section of this conversation 2.1. Scope for the catalogue and definition of “collection” (INFORMATION).
FYI, any work we do that results in enabling the community to define as needed (within scope), will also help other communities, such as library collections. The library community tried to develop a standard almost 20 years ago, and it was the at the point of this issue about grouping-the-groups in so many different ways, that they gave up on this part. See https://github.com/tdwg/cd/blob/master/reference/papers/CollectionDescriptionFocus_BriefingPaper_2002.pdf for their thinking (in parallel to ours) from 2002.