This is a Jellyfin problem; not a beets problem. You can easily solve it with beets config if you’d like to, though.
The distinction between what you want vs. what you’re getting is that Jellyfin is grouping by the “Artist” tag instead of the “Album Artist” tag. I haven’t touched Jellyfin in years, but look for a builtin setting or alternative view to group by album artist - you’ll almost certainly find it.
If you want to solve it in beets, you can do that through a custom script, the FtInTitle plugin, or a combo of the inline + advancedrewrite plugins. Remember to run a re-import on the Jellyfin side after making your tweaks to the beets pipeline to make your changes show up without duplication.
Object storage is indeed a specialized filesystem in a trenchcoat.
Object storage is typically (but not always) associated with non-hierarchical key-value lookups, as opposed to the directory tree pattern most file systems use. Object storage systems are also typically (but not always) designed with sharding and distribution in mind.