Choosing 'fast walking' and 'routes with fewest changes' sort of worked, but it still shows a walking route which doesn't use the pedestrian-only bridge:
Even with the fast walking, they seem to have employed a slow walker to measure this. My walk to work I can do in 35 mins, which isn't at a terribly fast pace, but even TfL's fastest option reports it as taking 44mins http://www.tfl.gov.uk/plan-a-journey/results?IsAsync=true&Jp...