He isn't obliged to know that. Not saying that's the case, but imagine a random guy, suddenly in town when the race passes by, who never watched a day of cycling before in his life but decides to join the fun and see what's about. Is he obliged to know that riders usually ride in places which seem alien to ride a bike to anyone who never watched the sport? I don't think the place where the crash takes place is part of the road also. From Google Street View images, that part is new and it seems to be more like a bike path than part of the actual road and, as cycling rules stands, riding is not allowed outside of the road proper.
If you see the video, right before he hits the person there is a barrier and, if you prolonged a line from that barrier to the crash site, that person is clearly before that imaginary line and is going back from the road as the riders come. When Lampaert turned from the cobbles to the tarmac, the person is already coming back to the side of the road but YL deviated faster.
Didn't this sector used to have barriers in the corners in the past, to prevent the riders from cutting the corner on the tarmac?