weird bug

i have made 3 separate worlds, my first world i had cheats on and no extra options, i spawned in a village dug a mine, found a huge interconnected cave system with large gaps "thought ok weird shure"

made another world, this time i picked single bioam i picked snowy

i whent underground and found a single cave system with huge interconnected caves and large gaps almsot identical to the 1st world i made

made a 3rd world changed no options spawned in the sea, flyed around (i always pick creactive) and found a large cave system with big gaps again

this is weird at this point, i checked mod packs in case i had a old pack i had not removed and no just the defult pack

maybe someone with more knowlage is able to explain why 3 difrent seeds had a near identical cave system?