I somehow made a parallel dimension???

So i was screwing around with some custom dimension procedures for my new mod (if you want more context let me know). I wanted to make a rift of sorts to enter the dimension. As of right now, it is a block, and there are two (one to get to the dimension, and one to go back to the overworld) That's not the interesting part however. When i placed the "Rift" down, the world around me looked incredibly familiar. And then i realized it was the exact same world, in another dimension.

Upon further testing, if the dimension has the fluid block set to air, magma blocks will not spawn in the other dimension in underwater caves, when they will in the overworld. Ores will also generate in the same place. It would seem that it's the exact same seed as the overworld, and i haven't done any extra coding at all.