As I understand it, both Beijing and Taipei maintain the fiction (or perhaps some in both capitals even believe it) that China is a single state, with one or more province(s) temporarily out of communion with the capitol. A large faction in Taipei would prefer to drop the fiction and “declare independence”, a notion that makes Beijing see red.
What if the Taipei regime were instead to dissolve itself, as the USSR did, letting sovereignty revert to the provinces? Beijing could hardly take that as the same kind of insult.