The answer is actually on FT already!
To quote from the 787 seating guide thread:
https://www.flyertalk.com/forum/british-airways-executive-club/1645350-seating-guide-boeing-787-dreamliner.html
(In the Wiki)
Boeing 787-9 seating comments:....The flush also uses a sensor rather than a button. This has potential to cause confusion at an inopportune moment