Bing,
Are you asking which year PADI allowed their DM's to teach Discover Scuba or are you implying DM (that are certified to teach Discover Scuba) are, as a
DM not allowed to perform a Discover Scuba?

If you are asking which year, I suggest you contact PADI yourself.
You should check the Instructor manual under Discover Scuba. It quotes,
under Member Qualifications. You do have a current PADI Instructor Guide, don't you?

Very encouraging... Your post appear argumentative.. Are you not happy?
Are you sour with life and people in general? Are you a know it all?
Try calming down a bit on your tone, in all your posts. Unless it is
the only way you can get people to post replies to yours.. This will be my last.