To me, that's the value of shadcn (conceptually) - it's nothing more than a tool to bootstrap your own UI library.

It let's you copy in snapshots and change/edit/refine as you go. You own the UI kit the moment you copy it in. I see Shadcn 'upgrades' as nothing more than a stranger's PR to my UI kit, which usually means useless noise, unless there's a specific feature/bug that I need.