They are not wakes, but speed indicators. I guess there was a choice to represent speed with length bars, as opposed to with color or numbers. Although I would expect length bars to be a natural choice made by a data scientists who is used to think of vectors as a bar with a length and a direction.
They aren't speed indicators, like how you would represent a vector field (e.g. in a quiver plot). If they were they would always be straight lines, and probably be arrows that point in the direction of travel.
The look like wakes. People will assume they are wakes.
