Nether things generate in overworld

I was playing in a roleplay world in a mountain biome when something red caught my eye i went over to it and it was a crimson tree.even weirder, i am in the area where i found it a LOT. this world was created between 1.14 and 1.15. so a nether tree somehow generated in an already generated place in the overworld. I showed it to my friend and she showed me a screen shot from a friends world.Apparently she had found a large..."clump" of warped and crimson stems.it was right behind her house and that area had already been generated. obviously a clump of nether stems is not something that naturally generates anywhere so there is some MAJOR generation bugs going on with the nether and overworld.