Not true. Perhaps it doesn’t apply to people who are not immediately visible as Taiwanese, but you may not refer to China as China because the CCP considers that implies you consider Taiwan as a separate entity. You cannot say you are from Taipei or any city either. You would have to add China in front of the city name. Same rule doesn’t apply to actual Chinese. So someone from Shanghai can just say I’m from Shanghai, but someone from Taipei would have to say I’m from China Taipei.
Here is Lin Yi-chen attending a Korean award show, and she says I’m from Taiwan in English, and it is translated as I’m from China Taiwan.
That’s Aboriginal singer Ye Wei-ting. At the time she can’t even say China Taiwan, she was forced to say China Taipei. Since she also wanted to say she is from Pingdong, she had to awkwardly say she is from China Taipei’s Pingdong region.