True.
But sometimes we want to test how a new update will migrate worlds that already exist. So we need a world that contains lots of complexity. The complexity often exposes issues that don’t exist on fresh worlds.
Also if we force a player reset of testing then it’s harder for players to test content later in the game.
I can see that as being an issue that could also be applied for a full wipe of the live servers too, which is what this post is suggesting.
Although I can see that a full ‘clean-slate’ reset of the test servers would essentially halt any further late/end game development as you’d have the inability to test them effectively without the complexity reasons you mentioned.