Well they are just concept illustrations in the form of graphs, but of course...
L=length -as in distance from the forward waterline of the board (could draw a picture of the board on the x axis)
And I have another picture, just to show how the waterline and high pressure area are moving constantly under the board in response to trim and waves.
My idea, which may be silly, is that the rough or dimpled surface may affect the time it takes for the high pressure area around the stagnation line (i.e., just behind the forward waterline) to shift in response to changes in water surface, board trim and flex (vice versa, etc....), and how far from the mean stagnation line it shifts, resulting in different accelerations imparted to the board and possibly more stable trim and/or less energy lost to flexing the board..
Normally we think of changing board's modulus, shape, or other physical properties to make the board react mechanically in a beneficial way.
Perhaps this different type of surface could contribute to getting the board to behave as we want it to by affecting how the forces are applied to the board in the first place.
Flex of a board is affected by sub-millimeter differences in thickness at key areas,
maybe similarly small differences in how forces are applied to a board also impact how it responds.
Whether dimples or striations of biaxial fiberglass really affect the situation in this way for better or worse, I really don't know.
Maybe someone will apply test tanks and FEA techniques to the question, as they do for aircraft and superyachts -but I don't know who would pay for that....