Yep, the SDO is quite primitive. It can be last or first coach and is a simple button press in the cab. If you go to Charing Cross you can see the signage/instruction for it.
The one I was on today made an auto announcement to say there would be a short platform. It is programed into the onboard PIS, rather than hardcoded into the SDO. Pretty simple update tbh.
Part of the reasons why the 700s get SDO at certain stations is because of the positioning of the new RLU/RLU boards. They are also shorter than the old stock they replaced. Because they had to add new boards/stop marks, they have to conform to the current standards (signal sighting requirements etc). So you get oddities like Elephant and Castle as well as Peckham Rye and Shoreham. Each of which will hold an 8 car Networker. Specific to Elephant, the 700 RLU is actually further forward than the 8 car DOO monitors.
As promised.. 4 Car just past the stairs at the end of the canopy. 5/6/8 London end.
Both a 6 and an 8 car went up there from Beckenham Junction today.