I could be wrong, but you might be confusing this with "strategic ambiguity" which afaik is keeping the PRC and ROC both guessing about how far the US will take its intervention. The "one china policy" wasn't ambiguous, it was a necessary step in order to create normal diplomatic relationships with the PRC. But once the US had normalized diplomatic relations with the PRC, it effectively said, "There is only one chain and the PRC is the legitimate government that we formally acknowledge." That is why all of these recent state visits between politicians in the US and Taiwan is so inflammatory. The US is only supposed to have "unofficial" ties to any other "government" that is supposed to represent China.