I feel this to be a balanced headline if we put on an editor’s hat: The subject of the sentence is "China." From China’s standpoint, Taiwan was always theirs. Hence, from this viewpoint, it is a "reclaim."
You would probably enjoy this lecture titled "the genesis of nations" from his history of Ukraine lecture: https://www.youtube.com/watch?v=0LaEmaMAkpM&list=PLh9mgdi4rN...
Thinking about this social form of the nation, what makes it particularly tricky, is that the nation once it exists, lays claim to the past.
The nation didn't already exist, but once it comes into existence, it tells a story about the past... This new social form has a story about how it's very old.
It's a lecture that explores questions about what a nation is, how that relates to governments, and how governments lay claim to a history, such as the history of China.
Here you point out that part of the KMT's history is rule over China, while CPC/CCP claim that same history yet Taiwan is not a part of CPC history, they never ruled it, only a part of "Chinese" history.
It wasn't a rebuttal or anything, I legitimately thought you might enjoy it since it questions some base assumptions about what a country/nation is and what your history is. Snyder loves word games and frequently references the deeper meanings of words as well as their unstated implications.