Some clarification, perhaps?
From my understanding of the reports in the Dutch press, the point of the experiment is aimed precisely at the package holiday sector. In the same way that the cruise holiday sector is thinking about vaccine 'passports' other, potentially more manageable tourism sectors, are trying to find ways to open up. In other words, the experiment is not intended to cover all possible ways of taking a holiday.
Consider the degree of public interest: 25,000 volunteers! Sfakia-lovers and such types are in the minority when it comes to tourism (thankfully). If anyone has had a chat with such people then you'll understand that, indeed, the country they visit is almost irrelevant to them. They want 1-3 weeks' worth of doing nothing much in a warm, sunny location. Spain (the costas, Canary islands), Greece (including Crete north coast tourism 'ghettos'), Turkey etc., it doesn't make much difference to them.
On the other hand, there are more than a few all-inclusive resorts that are as big as Sfakia, not just in terms of land cover but also in terms of occupant capacity. Whether or not anyone would feel trapped is a matter of preference and style. I've noticed more than a few people at places such as Loutro or Finix or even Sfakia who are quite content to spend all their time alternating between a small beach, one or more restaurants/cafes, and their hotel room. Even I can manage that for 3-4 days after a longer stretch of hiking. If there is a difference, it's not so much in the activity level, but in my own preference for a small village ambiance (combined with the hiking) rather than a big resort ambiance, and the fact that after several years my own personal routine has become subtly entwined with the lives of people living there.