What is the psychology behind laying out slabs at different angles for cyclists and pedestrians?

In the UK, we have many paths that are shared by pedestrians and cyclists, with a dividing line down the center to show who should be on which side of the path.

I noticed that at the end of such paths there are usually some different coloured slabs with ridges on them. Presumably these are just to alert people that the path is ending.

But I've noticed that on every path, the ridges are arranged differently for the cycle lane to the pedestrian lane- they always go parallel to the path for cylists, and perpendicular for pedestrians.

There is obviously a reason for this, since it appears to be universally applied. But I can't figure it out. I would have thought that it would make more sense to make the cyclists have the "bumpy" slabs, so they consciously notice that the shared path has now ended. As for pedestrians, I can't see why it should make a difference at all- maybe ridges across the path make it less slippery in the snow?

Can anyone suggest the actual reason?