I’d just add that you don’t necessarily need the “split”. It is useful for GNOME libs, because there’s a lot of them, and a lot of snaps using them.
Your library, including headers and such, could just live in a snap that the dependant can add to their build-snaps:, but also include the library itself in their snaps. The disadvantage, then, is that those dependants duplicate the library, and need rebuilding to include a new version. The advantage is that it’s simpler, and if the snaps come from different publishers, you don’t need to ask for auto-connection of that interface.
Hope that helps 