One of my goals when I started this project is that I would have one database for sightings and many taxonomies to interpret them. For example if (in some imagined world) I went to Kalidupa Island in 2019 and saw a scops owl, I would attach that sighting specifically to a kalidupae taxon and it would be filtered up to Moluccan Scops Owl in my IOC list and to Sulawesi Scops-Owl in my Clements list. And then when I looked at my lists later, after the 2022 updates had been applied I would see it as Moluccan in both lists. Without me having to go back and change my sighting.There are some truly messy groups. For example Asian Koel is split by BirdLife, but not by IOC or Clements. One of the subspecies is not recognized by IOC as it is synonomized with another subspecies. BirdLife however, recognize both the subspecies and the synonomized subspecies, but places them in separate species. How can you create a group for that unless you extend a list to include unrecognized subspecies, and update range info to facilitate recognition of the faux subspecies?
But those groups you're talking about, I think they correspond to what Denis LePage calls "taxonomic concepts". If you look at his Avibase site you can get an idea of what they are. For my kalidupae example he has five different "concepts" which describe its relationships; see Otus manadensis kalidupae (Sulawesi Scops-Owl (kalidupae)) - Avibase to look at them.