Folks, calm 
Here’s what we know from meetings with NIA:
- A gold card holder needs to do gold-card-like things during the term of their first card in order to qualify for a second card. (Source: NIA Gold Card Information Meeting, 2018)
- If qualifying under one of the the ‘salary’ criteria, the MoL will review your financial data (basically, your yearly tax return). If you do not pass the review, your work permit can be cancelled. (Source: Application Portal)
As @yyy mentioned, I believe (at least initially) the primary usage of this second clause will be to weed out people who have applied under false pretences. The warning’s appearance during the application process sends a clear message that one won’t get away with it for very long. Above all else, what governments want to avoid is embarrassment - an article that some group is rorting some aspect of a visa system would be particularly damaging to their current policy objectives.
So, what about the law-abiding people? Well, keep in mind that gold card holders may enter Taiwan without having a job at all. It’s entirely reasonable that a new immigrant would take some time to establish their network and find employment. Six-month job seeking visas are available, so that’s a tacit acknowledgement by the government that it does take some time. These people will still be subject to review.
The rules of administrative procedure in Taiwan require ‘fairness’ in their execution. Would it be ‘fair’ to cancel the work permit of a highly qualified individual who has taken six months to find a job, when others meeting lesser qualifications are given that time? Certainly not.
What about taking a break? Here, the length and circumstances of the break should probably be taken into account. Between jobs, or just feeling burned out and need a few months? Surely OK. However, if someone’s primary stated intention of gaining residence in Taiwan was employment (gold card), and they did not gain employment for, say, more than two years, does that stated intention still hold up? Maybe not. Or maybe the relevant authorities will consider point #1 from the beginning sufficient motivation for people (it was definitely seen in that light a couple years ago).
Keep in mind: there is some precedent for your visa going away if the underlying purpose for your residence in Taiwan no longer applies. Students who don’t turn up to class have sometimes found this out the hard way.
Though, don’t listen to the words of some random dude on the internet. If you are in a situation where you think your circumstances might put you in jeopardy, the gold card contacts list has a range of helpful people.