SELECT * FROM foo FOR SYSTEM_TIME AS OF ... should NOT include the Start and End timestamp columns because this acts like a normal query just with a different snapshot timestamp
SELECT * FROM foo FOR SYSTEM_TIME BETWEEN x AND y SHOULD include the Start and End timestamp columns since this form of query can include multiple row versions for the same row, so it makes sense to see the validity times
One disadvantage of returning system time columns is it
breaks upward compatibility. if an existing application wants to