World "world" regenerating

Hey, i own a server running on Paper 1.21.
I don't want the world "world" to be the main world, so i changed it in server.properties: level-name=survie
However, everytime i restart my server, "world" files are regenerated. The strange thing is that it is no longer considered as the level-name, because playerdata are stored in the "survie" world.
I use MultiverseCore for world management, but I don't think the problem is this plugin because it doesn't load the world in /mv list.
Do you have any idea where this could come from?
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