Ruined portals Generate underground

I generated world to find a ruined portal that could copy to structure block the first one I found generated underground, so tp'd to another and it was also underground. so generated a new world and that had portals underground. So generated a third and that one didn't as far as i could tell, but was curios now and generated a fourth and found all normal portals except for one underground that i found pretty far out. I don't know if the images will upload in the right order, but if they do,
seed for first image is -121918417815917811
seed for second image is 6496584387543080344
seed for third image is 6333840244786985795