Dripstone pillar in a river

I was again exploring a 21w37a world that i made and i found something strange. I found a dripstone block pillar, that was 9 blocks tall, starting from y=55 to y=64. It's also not a dripstone cave biome that generated above the ground, but just a dripstone pillar in a river biome. The seed is -7769170750943966983 and the cordinates are /execute in minecraft:overworld run tp @s 684.74 63.00 2900.64 612.75 18.00