Wouldn't that imply they recognize each other as different states? That is, if China considers Taiwan part of its territory, the Taiwanese are necessarily Chinese too. And equally the other way round.
UPDATE: notice that the question is about what they do to avoid implicit recognition of each other, but, at the same time deal with the fact that they de facto are two countries.
There are similarities in the West/East Germany divide, or regarding Spain/Gibraltar. The Spanish government, for example, can not refer to the 'border', but to the 'fence'.