I see what you are saying, but the language is confusing (which is no one’s fault, except possibly Taiwan’s and that of the people who translate the immigration laws into English).
There are no ROC or Taiwanese citizens, nor is there citizenship. Everyone is a national, either with or without housing registration, and they have nationality. I believe this has something to do with Taiwan’s complicated political situation, though I’m not an expert in this area. However, I do think because this distinction is very subtle, most people use the terms interchangeably.
When people who have at least one Taiwanese parent, but were never registered in Taiwan (because they were born overseas or to Taiwanese women and foreign men), talk about going back to Taiwan to get full nationality rights, it’s referred to as “reclaiming nationality”. Even the immigration agency uses this term. You are right that by definition a national shouldn’t need to reclaim nationality, but this is often how this process is described in English. Indeed, it really just means getting that ID number, and then having all the rights that an ordinary Taiwanese person might have.
Based on what you are saying, it seems there are a few ways for different kinds of people to apply for a TARC. However, I will repeat yet again, anyone who has an ROC passport (without household registration), must enter Taiwan on it to apply for the TARC. They check for the stamp and confirm it in their system when you make the application at the immigration office. Now, maybe someone who has an exit/entry permit and NO ROC passport can make an application for a TARC, but an ROC passport holder cannot.
Yes, the poster said he was an “overseas” Chinese. He didn’t need to say he was Taiwanese, because it’s very clearly implied: He has an ROC passport (but without an ID number). That means he’s an overseas Taiwanese. I suppose there may be exceptions to this rule. If you know of any, please share. But very usually, anyone with an ROC passport, but no registration, has a blood connection to Taiwan, or some special political connection (such as the KMT fighters from China who fled to Thailand after the civil war). And in any case, if you have an ROC passport, of any kind, and you are not in Taiwan, you are very much an overseas Taiwanese, by definition. I wasn’t being careless in this claim.
Now, perhaps you differentiate between being “Taiwanese” and being an “ROC national”. That’s a rather political matter, but I do feel that most people do not make this distinction. For the purposes here, I am using the terms interchangeably.
Indeed, this conversation of the TARC has strayed to one of establishing nationality (which is the same, bureaucratically-speaking, as getting an ID card/number or getting household registration). This is not an illogical progression, despite being a diversion. The poster mentions that he cannot at this time spend the year needed to get full rights, so clearly, he has considered it.
I have already argued that I don’t think it’s worth it for someone who does not live in Taiwan to bother getting a TARC, unless they were planning to put in the time to get full nationality rights. Perhaps you can move the conversation forward with reasons why it would be worth it.