Something with how the freeze top layer function works makes it so that every structure generated on the surface has a snow layer inside on the floor. Mainly found this because of structure mods but it seems to happen the same way with vanilla villages as well.
This is generally intended - it's how snow creeps inside cave entrances, under overhangs, and is part of primal winter's more aggressive snowfall world generation.
Something with how the freeze top layer function works makes it so that every structure generated on the surface has a snow layer inside on the floor. Mainly found this because of structure mods but it seems to happen the same way with vanilla villages as well.