Both of the examples shown here seem to be horizontal scans, whereas the images I most associate with slit-scan are vertical scans like the old auto racing shots where the wheels look elliptical. Really, it's about the movement of the slit relative to the movement of the objects. If they are in the same plane, you just get compression or stretching. If they are in different planes, you get skewing which is (to me) more traditional.
For this reason, the shadows in the first picture don't actually show the direction of motion. They are merely compressed versions of the actual shadows.
For the bike race, the horizontal scan makes sense because it magnifies the wheel position.
EDIT: wait a sec, that's not entirely right. I might need to read up on this particular slit-scan a bit more.