What you say is irrelevant. The PRC may annex the ROC someday (militarily or by other means), but that wouldn't change the fact that between 1949 and until that happens that there were two separate countries. The UN doesn't make countries it's just a forum that some governments are invited to be a part of. The political status of the ROC is just as simple as that as the PRC. To say otherwise is what actually is disingenuous.
> Your line of argument also doesn't actually address the original point, which is that China tolerates the independence of Hong Kong because it has its sights set on Taiwan - which is the real prize.
Yes taking over the ROC is the real prize because right now it is _independent_ and the PRC wants that to change. The mental somersaults you do to avoid saying this obvious truth is mind boggling.
> From that perspective, it doesn't matter how Taiwan sees itself.
This is true! The ROC claims the territories of the mainland as well as Mongolia in its constitution. This is delusional. Similarly the PRC claims the mainland and the ROC's territories as its own. This is also delusional. It matters how neither side officially sees themselves. They _are_ two separate countries.
Why can't you just admit that the PRC has imperialistic ambitions and tries to make up justifications to make the PRC look like it is in the right? Why are you so hellbent to ignore reality?