this i haven't encountered myself, but i did see it from a stream
there was a guy in twitch's chat saying that when they set trees to "lots" it spawned some trees from Ship Wrecked dispite making a fresh RoG world.
the streamer (flareV2) decided to do science and set everything to "lots" in a new world, and also decided to set everything from SW to "lots"
fishermerms and poison everywhere
and Prime apes
1.) set trees to lots(this works with everything, but trees are the most safe thing) in a RoG world (not tested with vanilla) 2.) generate world