I… would also have thought this as well.

Just have a player host their own instance, everyone connects to them, and have some kind of fallback system in place in case the host disconnects.

Then, next step, make it so that once that basic framework is setup, maybe also have a basic host migration thing within an established group of players, basically ping everyone to everyone and pick the person who has the lowest average ping to everyone else as the host.

I do not undertand at all why this game … needs a central server at all.

It is described as an ‘online only’ game.

I have not played it, but it seems like the levels are small, the default player count is 6, but a lot of the game is based on physics interactions…

Closest comparison I can think of is fucking about on GMod with 6 people, which you could probably pull off with your own self hosted instance, but a higher player count (which is apparently the main thrust of these mods that they say are anihilating their bandwidth) would need an actual dedicated server to avoid desync and lagging into oblivion.