I might point out that “succeeding” and “being allowed to form a separate state” are two wholly different things. One succeeds on your own, when you must ask a different power to let you go it isn’t succession. Compare both of your examples to the Southern State’s succeeding from the Union. They didn’t ask the Union’s permission, they exerted sovereign authority and succeeded. So I appreciate all the West Virginia and Vermont examples but NEITHER of those are a succession.