The kit supplied sprockets are not designed to be "hub centric" or self centering Cavi, there's far too many different hub sizes for that to be feasible, let alone the different sprocket manufacturers & their questionable quality control.
While it would be nice if they were and the idea of making an adapter ring isn't a bad one - the fact is the vast majority of the rag joint sprockets installed by our members have no adapter ring and as the sprocket's center hole is too large in most cases they're adjusted and centered by hand, with a gap between the sprocket's center hole and the hub.
Every one I've installed has at least 1/16" gap or more and yet when properly adjusted and toqued they have remained in place without shifting - while I'm not a huge fan of the rag joint method of adding a sprocket, they are more than strong enough to prevent the sprocket from shifting.
Simply put, your advice isn't always accurate either. Like you, folks are simply trying to offer whatever experience they've managed to acquire - I suspect there's no such thing as an "expert" in that there's always something more to learn, someone else that's done something differently and there will always be someone that knows more.
I would ask that you remember that when replying.