You are correct on that is a class D extension. I am a little confused on how the person in the FAA is making the determination that doesn't require an authorization? Part 107 states Class E to the surface requires an authorization.
Step 2B – Controlled Airspace Requests
If you want to fly in controlled airspace (Class B, C, D, or surface area E), you will need to
apply for an airspace authorization or airspace waiver.
I see nothing in the actual regulations stating anything difference? I am going to contact my local FSDO and see just what they say on this. I am now curious myself. The extension on MFR, Medford is a class E2, this does require this even in the memo you have posted. I am not saying you are wrong, just the regulations are not stating this? I want to see how my FSDO decides on the memo until the regulaton itself is changed. Having been in the aviation industry for a long time I have found what one FSDO interprets and another may be totally different views. I personally want to know how my FSDO views this before I venture in to the surface class E without out authorization.
I just went on the FAA.GOV website and it still states Class E surface area which is the dashed magenta lines on a sectional chart does require authorization. It does not state anything about it being linked directly to the class D airspace. Here is a copy taken directly from the FAA.GOV site under regulations. I personally hope the Memo you link goes to is correct and my FSDO has the same view.
THE IMPACT TO AIR TRAFFIC CONTROL
After the effective date, those operators that have successfully passed the required knowledge test and received a remote pilot certificate may begin operations in Class G airspace at or below 400 AGL without contacting ATC or issuing a NOTAM.
For operations in controlled airspaces (Class B, C and D airspace, and E surface area) the Air Traffic Organization, in collaboration with NATCA, is establishing a process where the operator can make a request and receive approval through an automated system. The operators will not contact individual ATC facilities to make the request. ATC guidance, procedures, polices and processes are under development and will be available prior to the effective date of the rule. For more information on the new rule visit the FAA UAS website at
www.FAA.gov/UAS. MAJOR PROVISIONS
Unmanned aircraft must weigh less than 55 lbs. (25 kg) Visual line-of-sight (VLOS) only; the unmanned aircraft must remain within VLOS of the remote pilot in command and the person manipulating the flight controls of the small UAS Small unmanned aircraft may not operate over any persons not directly participating in the operation, not under a covered structure, and not inside a covered stationary vehicle Daylight-only operations or civil twilight (30 minutes before official sunrise to 30 minutes after official sunset, local time) with appropriate anti-collision lighting Must yield right-of-way to other aircraft May use visual observer (VO) but not required Maximum groundspeed of 100 mph (87 knots)
Maximum altitude of 400 feet above ground level (AGL) or, within 400 feet of a structure, 400 feet above that structure Minimum weather visibility of 3 miles from control station and must remain 500 feet from clouds (no ceiling requirement)
Operations in Class B, C, D and Class E surface areas are allowed with ATC approval Operations in Class G airspace are allowed without ATC permission sUAS cannot be operated from a moving aircraft sUAS cannot be operated from a moving vehicle unless the operation is over a sparsely populated area No careless or reckless operations No carriage of hazardous materials FAA airworthiness certification is not required