They say what the PRC forces them to say but de facto don’t believe in it. It’s a complete misrepresentation to argue that Taiwan agree with China regarding reunification but with reversed roles.
Taiwan is a democracy and a majority of Taiwanese want independence but argue for keeping the status quo in order to avoid a war (both the KMT and the DDP - their disagreement is more technical than that). Some wanted Taiwan to declare it in the 90s to force the hand of the USA and win a decisive war but this position seems more precarious nowadays.
No, its not. If I point a gun to your head, and tell you that I am going to shoot you, if you do not "agree" that the moon is made of cheese, you are not actually "agreeing".
We both know, that you do not agree that the moon is made of cheese, in this situation. I have just made words come out of your mouth, to something that you do not agree with.
To say that they "agree" is just a silly word game, that does not reflect the truth of the matter, and instead is playing into propaganda that denies the reality that Taiwan is already a country, and is already independent of china, and that Taiwan is not interesting in being taken over, or taking over china.