There are suspicions that Taiwan is already a nuclear nation. So are S Korea, Japan, Iran, Turkey, S Africa and Brazil. Almost all W European nations can become nuclear as soon as necessary. So can Argentina, Australia, Egypt and Indonesia.
All areas you have mention have singed NPT and cannot test unless they take legal remedy. Taiwan on otherhand face no issue. Surely PRC will enact a law and say Taiwan cannot test without its permission (lol) like how they cannot declare independence.
Try and delve to a more contemporary calculation by using the 1992 consensus between PRC and ROC on One China where the non definition of a stutus is evident by having a status quo in place*
A status quo determines and quantifies stability and no change
If one side has nukes the other must also it is after all STATUS QUO !!
The only way to stop such thoughts for PRC say it wants to take over Taiwan and break up the 1992 consesus ... Even trying defining the 1992 consensus needs to have a status where PRC has to say it will take over Taiwan (emboldened USA nuke protection in any case)
And
Taiwan has nuclear plants and stockpiles
south Korea and Japan have USA nuclear protection (unclear will take benefit of doubt).
Taiwan does it have nuclear protection from USA
Why else PRC not unified with it already ... Do we say PRC military is conventional not capable to take on Taiwan military (sure the nearest area of taiwan is in PRC border) and taiwan proud how it defended against PRC over there on that island
The USA has a law for protection of taiwan does that mean nuclear protection. Surely in affirmative (but it still evades that question on testing)
IAEA into taiwan is done from USA not PRC ironic and through some unwritten mechnaisim. ***** Taiwan helped us (India) with our nuclear position (look how Australia and Japan provide to taiwan outside NPT)
Has Taiwan signed NPT ... Such questions not good for the eyes for PRC (it did but why prc signed and tested nukes and if it did not why IAEA by way of usa)
The PRC prides it self on taking advantage of grey definitions
There one sitting right across its face where Taiwan can test and help the region maintain a STATUS QUO
1970s also did not have 1992 consensuses. And no testing by North Korea (and Pakistan - you know taiwan and India super computing collimation).
Can India rent the Taiwan nuclear testing status for a few days please ... Sometimes I think they will lend it in kind : )
North Korea roll on the floor and laugh