While a previous government of Taiwan claimed that it was the legitimate ruler of China, the current government does not. It considers itself to be a separate sovereign state. The KMT that fought for control of China and fled the mainland is only a small fraction of Taiwan's population and only ruled over the majority by political suppression.

This is a clear tell that your knowledge of the situation is basically just Wikipedia plus media reporting. Approximately nobody in Taiwan views it that way. It is an obscure legal fiction of no relevance. It only persists because of a red line drawn by the PRC.

It’s kind of like how New Zealand is included as a province of Australia, technically, in their constitution.

Not very wrong but maybe at least half of population will not agree with that