I went by a couple of times yesterday and that button is actually the pedestrian button to cross along Gladstone, there due to silly HTA rules. Bikes change it by stupid yellow dots, of course. I mind them less on bike routes than on roads.
The light does seem to change super quickly. The second time i went by I pressed the button and the countdown immediately went to five (FIVE) seconds and then I got the cross light. WHAT??? I am amazed.