The thing with the various double taxation treaties is that they introduce limits to the laws in the participating countries: So while in principle everyone staying in Taiwan longer than 90 days will have to pay taxes, a double taxation treaty might restrict this regulation from being applied.
However, the rules with those double taxation treaties are much less easy to follow. They highly depend on the agreement and might leave some room for interpretation. So they are usually impossible to navigate without the help of professional tax advisors and/or lawyers. In some cases, the local tax authorities might actually be able to help - but they might be biased in some way.
So in theory, there could be some situations where someone stays in Taiwan for an entire year and doesn’t have to pay taxes here, but rather in their home country if there is a double taxation treaty in place which allows that and basically acts as a limit to Taiwan‘s tax laws.
For example, see the taxation treaty between the UK and Taiwan:
a) he shall be deemed to be a resident only of the territory in which he has a permanent home available to him; if he has a permanent home available to him in both territories, he shall be deemed to be a resident only of the territory with which his personal and economic relations are closer (centre of vital interests);
b) if the territory in which he has his centre of vital interests cannot be determined, or if he does not have a permanent home available to him in either territory, he shall be deemed to be a resident only of the territory in which he has an habitual abode;
c) if the individual has an habitual abode in both territories or in neither of them, the competent authorities of the territories shall settle the question by mutual agreement.
That means if you would be liable to pay taxes in both the UK and Taiwan (important: If you‘re not a resident of the UK and Taiwan at the same time, the treaty won’t even be applied!), the taxation treaty would answer the question in which country you actually need to pay taxes. If you still have a permanent home in the UK and your „center of vital interest“ clearly lays in the UK, you can stay in Taiwan tax free and pay taxes in the UK as long as you want.
However, if the Taiwanese authorities doubt that (maybe by arguing that you spent the majority of the year in Taiwan), it might easily end up with the situation ( see part c) where it‘s basically up to the tax authorities to make a decision (and the taxpayer potentially using a lawyer to object that decision).
Also, the tax treaties usually contain some other specifics and exceptions (for example that other rules might apply when having a local employer in only one of the countries) which can easily introduce a situation where you would still need to pay taxes in another country.
So it’s really not that easy, unfortunately…