When chunks are created, I often see mobs such as cows, foxes, etc. spawn some distance in the air and fall into the ocean. This happens in a world that was created in 1.8.1 and updated over the years to 1.19. No one has explored new land since the 1.18 update so I don't know whether or not this began in 1.18 or 1.19. I'm also not sure whether this is an issue with old maps or an issue that occurs in all maps.
Region files have previously been deleted from this save file to reduce its size. (Presumed to be cleaner than using a world editing program.) It's possible that these occurrences are happening in areas where terrain was generated in a previous version, then deleted. I don't think this is related, but I'm mentioning it for the sake of being thorough.
Please close this issue. I found the cause. Entities used to be saved in region files but are now in separate files. These were not deleted so the new land kept the old mobs. Re-trimming the world, this time including poi and entity files, should resolve the issue. Minecraft is probably working as intended.