I'm not sure how you define threaten, but I think that firing missiles over the island during election season (https://en.wikipedia.org/wiki/Third_Taiwan_Strait_Crisis) definitely counts as a threatening act. China has made so many threats about taking back Taiwan by force that I don't know how anybody could miss it. It's one thing to think that ROC is part of PRC (it's not), but it's another level of stubbornness to think that Taiwan is not threatened by Mainland China.