Mike A ,
It is easy enough to offset the chamber, but the bore would be centered at the muzzel.It would complicate,some, the threading to locate the chamber at "top dead center"(or I guess "bottom dead center") so the offset bore would require adjustment to the sight heights instead of windage.There may be other reasons,important to whoever is doing the work.Of course if both rimfire and centerfire barrels will be fit to the same action,offsetting the rimfire chamber is necessary.
Mike