And I'd like to point out that the ROC and the PRC don't even have the same land claims. The PRC claims the mainland and Taiwan. The ROC claims the mainland, Taiwan, and Mongolia. Mongolia claims Mongolia. There are three separate countries making these claims.
The fact that (some of) their claims overlap doesn't magically mean that the ROC and PRC aren't two separate countries. It just means that they are two countries that claim more land than they control.
This is very much outdated and a relic of the times when anti-communist world powers believed they could maybe remove communism from mainland china. It is a believe held today only by a small minority. https://www.taiwannews.com.tw/en/news/3951560
And I'd like to point out that the ROC and the PRC don't even have the same land claims. The PRC claims the mainland and Taiwan. The ROC claims the mainland, Taiwan, and Mongolia. Mongolia claims Mongolia. There are three separate countries making these claims.
The fact that (some of) their claims overlap doesn't magically mean that the ROC and PRC aren't two separate countries. It just means that they are two countries that claim more land than they control.