I'm not quite sure why it does that but I noticed that also.

I now make it a habit to review the code before any changes and getting rid of "risky" stuff like unnecessary drops and creates. At least in the code I've seen, it always seems to create a table with a temp name with the same or new schema (I think it does this blindly), copies the data to the new table, then drops the old table, and lastly renames the new table with the old table name.