The author doesn’t support his claim that a nuclear armed Taiwan would have been destabilizing.
I think an argument can be made for that though, and it rests on the fact that China wouldn’t mind losing a few cities but it would mind losing a lot of cities.
If Taiwan developed a nuke and it became public before Taiwan built enough nukes to destroy China, then China might have decided it is better to act now rather than later.
Historically China, with its huge population, has shown a willingness to throw bodies at military problem because they figure they can always get more. Losing a few million civilians to gain control of Taiwan wouldn’t be a difficult choice.