Oh, that's a bunch of BS about expecting "walking speeds" in the crosswalk. A car that sees a bike in the cross walk won't expect anything of which you say. It's not like once you get into a car you lose all depth perception and all ability to judge relative speed.
What's likely to happen is if you are travelling against traffic in a cross walk, cross traffic won't look in your direction (your right turning motorist won't look to his right) and may hit you. This happens to me all the time as a pedestrian and makes me want to carry a bike flag so I can wave it in front of cars who aren't looking my way.