It sounds to me like this whole thing is based on Paul Eggert trying to preemptively avoid the political question of "what is a country?". He says in one of the threads [1]:

  There is a distinction, though, between tz mailing-list politics (the focus of much of the recent
  discussion) and real-world politics (things like, "is Kosovo a country?"). My main worry is the
  latter not the former, in that I think it's worth making minor technical changes to tzdb now to
  help forestall potentially major real-world political problems down the road, problems
  that could be worse than being sued by astrologers. Admittedly not everyone sees things this way.

...the elephant no one seems to be talking about as the canonical example of the question is Taiwan.

Rather than get wrapped around the political axle of whether Taiwan counts as a country for purposes of inclusion in the timezone db, it sounds like he wants to just set up a system where tzdb says "here's a time zone that's identified by its biggest city." That way if Taiwan is listed, it's only because it happened to be the biggest city in its timezone, not because the tzdb is making any political statement about its political status.

That's understandable from a certain point of view, but I think it's doomed to failure for a couple reasons:

1) the tzdb never did this in the past, so it's a huge change to the default behavior. Changing the world's timezone names is an enormous change, that will break an f-ton of stuff, so downstream folks are understandably unhappy about it. The moment something important breaks because a system couldn't find "US/Eastern" is the moment this either gets reverted or forked.

2) You may not want to play the political game, but it wants to play with you. City/territory names aren't neutral, either, and are just as political (Derry/Londonderry), so relying on city names doesn't actually solve the problem, it just makes it less likely.

I suspect they're going to have to stick with countries, and let IANA make the determination of what's a country, so they don't have to have gigantic political fights, they can defer to IANA policy.

[1]: https://mm.icann.org/pipermail/tz/2021-June/030177.html